1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 1994 Linus Torvalds
4 *
5 * Cyrix stuff, June 1998 by:
6 * - Rafael R. Reilova (moved everything from head.S),
7 * <rreilova@ececs.uc.edu>
8 * - Channing Corn (tests & fixes),
9 * - Andrew D. Balsa (code cleanup).
10 */
11 #include <linux/init.h>
12 #include <linux/utsname.h>
13 #include <linux/cpu.h>
14 #include <linux/module.h>
15 #include <linux/nospec.h>
16 #include <linux/prctl.h>
17 #include <linux/sched/smt.h>
18 #include <linux/pgtable.h>
19 #include <linux/bpf.h>
20
21 #include <asm/spec-ctrl.h>
22 #include <asm/cmdline.h>
23 #include <asm/bugs.h>
24 #include <asm/processor.h>
25 #include <asm/processor-flags.h>
26 #include <asm/fpu/api.h>
27 #include <asm/msr.h>
28 #include <asm/vmx.h>
29 #include <asm/paravirt.h>
30 #include <asm/alternative.h>
31 #include <asm/set_memory.h>
32 #include <asm/intel-family.h>
33 #include <asm/e820/api.h>
34 #include <asm/hypervisor.h>
35 #include <asm/tlbflush.h>
36
37 #include "cpu.h"
38
39 static void __init spectre_v1_select_mitigation(void);
40 static void __init spectre_v2_select_mitigation(void);
41 static void __init retbleed_select_mitigation(void);
42 static void __init spectre_v2_user_select_mitigation(void);
43 static void __init ssb_select_mitigation(void);
44 static void __init l1tf_select_mitigation(void);
45 static void __init mds_select_mitigation(void);
46 static void __init md_clear_update_mitigation(void);
47 static void __init md_clear_select_mitigation(void);
48 static void __init taa_select_mitigation(void);
49 static void __init mmio_select_mitigation(void);
50 static void __init srbds_select_mitigation(void);
51 static void __init l1d_flush_select_mitigation(void);
52
53 /* The base value of the SPEC_CTRL MSR without task-specific bits set */
54 u64 x86_spec_ctrl_base;
55 EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
56
57 /* The current value of the SPEC_CTRL MSR with task-specific bits set */
58 DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
59 EXPORT_SYMBOL_GPL(x86_spec_ctrl_current);
60
61 static DEFINE_MUTEX(spec_ctrl_mutex);
62
63 /*
64 * Keep track of the SPEC_CTRL MSR value for the current task, which may differ
65 * from x86_spec_ctrl_base due to STIBP/SSB in __speculation_ctrl_update().
66 */
write_spec_ctrl_current(u64 val,bool force)67 void write_spec_ctrl_current(u64 val, bool force)
68 {
69 if (this_cpu_read(x86_spec_ctrl_current) == val)
70 return;
71
72 this_cpu_write(x86_spec_ctrl_current, val);
73
74 /*
75 * When KERNEL_IBRS this MSR is written on return-to-user, unless
76 * forced the update can be delayed until that time.
77 */
78 if (force || !cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
79 wrmsrl(MSR_IA32_SPEC_CTRL, val);
80 }
81
spec_ctrl_current(void)82 u64 spec_ctrl_current(void)
83 {
84 return this_cpu_read(x86_spec_ctrl_current);
85 }
86 EXPORT_SYMBOL_GPL(spec_ctrl_current);
87
88 /*
89 * AMD specific MSR info for Speculative Store Bypass control.
90 * x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu().
91 */
92 u64 __ro_after_init x86_amd_ls_cfg_base;
93 u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;
94
95 /* Control conditional STIBP in switch_to() */
96 DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp);
97 /* Control conditional IBPB in switch_mm() */
98 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb);
99 /* Control unconditional IBPB in switch_mm() */
100 DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb);
101
102 /* Control MDS CPU buffer clear before returning to user space */
103 DEFINE_STATIC_KEY_FALSE(mds_user_clear);
104 EXPORT_SYMBOL_GPL(mds_user_clear);
105 /* Control MDS CPU buffer clear before idling (halt, mwait) */
106 DEFINE_STATIC_KEY_FALSE(mds_idle_clear);
107 EXPORT_SYMBOL_GPL(mds_idle_clear);
108
109 /*
110 * Controls whether l1d flush based mitigations are enabled,
111 * based on hw features and admin setting via boot parameter
112 * defaults to false
113 */
114 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
115
116 /* Controls CPU Fill buffer clear before KVM guest MMIO accesses */
117 DEFINE_STATIC_KEY_FALSE(mmio_stale_data_clear);
118 EXPORT_SYMBOL_GPL(mmio_stale_data_clear);
119
check_bugs(void)120 void __init check_bugs(void)
121 {
122 identify_boot_cpu();
123
124 /*
125 * identify_boot_cpu() initialized SMT support information, let the
126 * core code know.
127 */
128 cpu_smt_check_topology();
129
130 if (!IS_ENABLED(CONFIG_SMP)) {
131 pr_info("CPU: ");
132 print_cpu_info(&boot_cpu_data);
133 }
134
135 /*
136 * Read the SPEC_CTRL MSR to account for reserved bits which may
137 * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
138 * init code as it is not enumerated and depends on the family.
139 */
140 if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
141 rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
142
143 /* Select the proper CPU mitigations before patching alternatives: */
144 spectre_v1_select_mitigation();
145 spectre_v2_select_mitigation();
146 /*
147 * retbleed_select_mitigation() relies on the state set by
148 * spectre_v2_select_mitigation(); specifically it wants to know about
149 * spectre_v2=ibrs.
150 */
151 retbleed_select_mitigation();
152 /*
153 * spectre_v2_user_select_mitigation() relies on the state set by
154 * retbleed_select_mitigation(); specifically the STIBP selection is
155 * forced for UNRET or IBPB.
156 */
157 spectre_v2_user_select_mitigation();
158 ssb_select_mitigation();
159 l1tf_select_mitigation();
160 md_clear_select_mitigation();
161 srbds_select_mitigation();
162 l1d_flush_select_mitigation();
163
164 arch_smt_update();
165
166 #ifdef CONFIG_X86_32
167 /*
168 * Check whether we are able to run this kernel safely on SMP.
169 *
170 * - i386 is no longer supported.
171 * - In order to run on anything without a TSC, we need to be
172 * compiled for a i486.
173 */
174 if (boot_cpu_data.x86 < 4)
175 panic("Kernel requires i486+ for 'invlpg' and other features");
176
177 init_utsname()->machine[1] =
178 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
179 alternative_instructions();
180
181 fpu__init_check_bugs();
182 #else /* CONFIG_X86_64 */
183 alternative_instructions();
184
185 /*
186 * Make sure the first 2MB area is not mapped by huge pages
187 * There are typically fixed size MTRRs in there and overlapping
188 * MTRRs into large pages causes slow downs.
189 *
190 * Right now we don't do that with gbpages because there seems
191 * very little benefit for that case.
192 */
193 if (!direct_gbpages)
194 set_memory_4k((unsigned long)__va(0), 1);
195 #endif
196 }
197
198 /*
199 * NOTE: This function is *only* called for SVM. VMX spec_ctrl handling is
200 * done in vmenter.S.
201 */
202 void
x86_virt_spec_ctrl(u64 guest_spec_ctrl,u64 guest_virt_spec_ctrl,bool setguest)203 x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest)
204 {
205 u64 msrval, guestval = guest_spec_ctrl, hostval = spec_ctrl_current();
206 struct thread_info *ti = current_thread_info();
207
208 if (static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) {
209 if (hostval != guestval) {
210 msrval = setguest ? guestval : hostval;
211 wrmsrl(MSR_IA32_SPEC_CTRL, msrval);
212 }
213 }
214
215 /*
216 * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update
217 * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.
218 */
219 if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
220 !static_cpu_has(X86_FEATURE_VIRT_SSBD))
221 return;
222
223 /*
224 * If the host has SSBD mitigation enabled, force it in the host's
225 * virtual MSR value. If its not permanently enabled, evaluate
226 * current's TIF_SSBD thread flag.
227 */
228 if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
229 hostval = SPEC_CTRL_SSBD;
230 else
231 hostval = ssbd_tif_to_spec_ctrl(ti->flags);
232
233 /* Sanitize the guest value */
234 guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;
235
236 if (hostval != guestval) {
237 unsigned long tif;
238
239 tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :
240 ssbd_spec_ctrl_to_tif(hostval);
241
242 speculation_ctrl_update(tif);
243 }
244 }
245 EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);
246
x86_amd_ssb_disable(void)247 static void x86_amd_ssb_disable(void)
248 {
249 u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask;
250
251 if (boot_cpu_has(X86_FEATURE_VIRT_SSBD))
252 wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD);
253 else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD))
254 wrmsrl(MSR_AMD64_LS_CFG, msrval);
255 }
256
257 #undef pr_fmt
258 #define pr_fmt(fmt) "MDS: " fmt
259
260 /* Default mitigation for MDS-affected CPUs */
261 static enum mds_mitigations mds_mitigation __ro_after_init = MDS_MITIGATION_FULL;
262 static bool mds_nosmt __ro_after_init = false;
263
264 static const char * const mds_strings[] = {
265 [MDS_MITIGATION_OFF] = "Vulnerable",
266 [MDS_MITIGATION_FULL] = "Mitigation: Clear CPU buffers",
267 [MDS_MITIGATION_VMWERV] = "Vulnerable: Clear CPU buffers attempted, no microcode",
268 };
269
mds_select_mitigation(void)270 static void __init mds_select_mitigation(void)
271 {
272 if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) {
273 mds_mitigation = MDS_MITIGATION_OFF;
274 return;
275 }
276
277 if (mds_mitigation == MDS_MITIGATION_FULL) {
278 if (!boot_cpu_has(X86_FEATURE_MD_CLEAR))
279 mds_mitigation = MDS_MITIGATION_VMWERV;
280
281 static_branch_enable(&mds_user_clear);
282
283 if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) &&
284 (mds_nosmt || cpu_mitigations_auto_nosmt()))
285 cpu_smt_disable(false);
286 }
287 }
288
mds_cmdline(char * str)289 static int __init mds_cmdline(char *str)
290 {
291 if (!boot_cpu_has_bug(X86_BUG_MDS))
292 return 0;
293
294 if (!str)
295 return -EINVAL;
296
297 if (!strcmp(str, "off"))
298 mds_mitigation = MDS_MITIGATION_OFF;
299 else if (!strcmp(str, "full"))
300 mds_mitigation = MDS_MITIGATION_FULL;
301 else if (!strcmp(str, "full,nosmt")) {
302 mds_mitigation = MDS_MITIGATION_FULL;
303 mds_nosmt = true;
304 }
305
306 return 0;
307 }
308 early_param("mds", mds_cmdline);
309
310 #undef pr_fmt
311 #define pr_fmt(fmt) "TAA: " fmt
312
313 enum taa_mitigations {
314 TAA_MITIGATION_OFF,
315 TAA_MITIGATION_UCODE_NEEDED,
316 TAA_MITIGATION_VERW,
317 TAA_MITIGATION_TSX_DISABLED,
318 };
319
320 /* Default mitigation for TAA-affected CPUs */
321 static enum taa_mitigations taa_mitigation __ro_after_init = TAA_MITIGATION_VERW;
322 static bool taa_nosmt __ro_after_init;
323
324 static const char * const taa_strings[] = {
325 [TAA_MITIGATION_OFF] = "Vulnerable",
326 [TAA_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
327 [TAA_MITIGATION_VERW] = "Mitigation: Clear CPU buffers",
328 [TAA_MITIGATION_TSX_DISABLED] = "Mitigation: TSX disabled",
329 };
330
taa_select_mitigation(void)331 static void __init taa_select_mitigation(void)
332 {
333 u64 ia32_cap;
334
335 if (!boot_cpu_has_bug(X86_BUG_TAA)) {
336 taa_mitigation = TAA_MITIGATION_OFF;
337 return;
338 }
339
340 /* TSX previously disabled by tsx=off */
341 if (!boot_cpu_has(X86_FEATURE_RTM)) {
342 taa_mitigation = TAA_MITIGATION_TSX_DISABLED;
343 return;
344 }
345
346 if (cpu_mitigations_off()) {
347 taa_mitigation = TAA_MITIGATION_OFF;
348 return;
349 }
350
351 /*
352 * TAA mitigation via VERW is turned off if both
353 * tsx_async_abort=off and mds=off are specified.
354 */
355 if (taa_mitigation == TAA_MITIGATION_OFF &&
356 mds_mitigation == MDS_MITIGATION_OFF)
357 return;
358
359 if (boot_cpu_has(X86_FEATURE_MD_CLEAR))
360 taa_mitigation = TAA_MITIGATION_VERW;
361 else
362 taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;
363
364 /*
365 * VERW doesn't clear the CPU buffers when MD_CLEAR=1 and MDS_NO=1.
366 * A microcode update fixes this behavior to clear CPU buffers. It also
367 * adds support for MSR_IA32_TSX_CTRL which is enumerated by the
368 * ARCH_CAP_TSX_CTRL_MSR bit.
369 *
370 * On MDS_NO=1 CPUs if ARCH_CAP_TSX_CTRL_MSR is not set, microcode
371 * update is required.
372 */
373 ia32_cap = x86_read_arch_cap_msr();
374 if ( (ia32_cap & ARCH_CAP_MDS_NO) &&
375 !(ia32_cap & ARCH_CAP_TSX_CTRL_MSR))
376 taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;
377
378 /*
379 * TSX is enabled, select alternate mitigation for TAA which is
380 * the same as MDS. Enable MDS static branch to clear CPU buffers.
381 *
382 * For guests that can't determine whether the correct microcode is
383 * present on host, enable the mitigation for UCODE_NEEDED as well.
384 */
385 static_branch_enable(&mds_user_clear);
386
387 if (taa_nosmt || cpu_mitigations_auto_nosmt())
388 cpu_smt_disable(false);
389 }
390
tsx_async_abort_parse_cmdline(char * str)391 static int __init tsx_async_abort_parse_cmdline(char *str)
392 {
393 if (!boot_cpu_has_bug(X86_BUG_TAA))
394 return 0;
395
396 if (!str)
397 return -EINVAL;
398
399 if (!strcmp(str, "off")) {
400 taa_mitigation = TAA_MITIGATION_OFF;
401 } else if (!strcmp(str, "full")) {
402 taa_mitigation = TAA_MITIGATION_VERW;
403 } else if (!strcmp(str, "full,nosmt")) {
404 taa_mitigation = TAA_MITIGATION_VERW;
405 taa_nosmt = true;
406 }
407
408 return 0;
409 }
410 early_param("tsx_async_abort", tsx_async_abort_parse_cmdline);
411
412 #undef pr_fmt
413 #define pr_fmt(fmt) "MMIO Stale Data: " fmt
414
415 enum mmio_mitigations {
416 MMIO_MITIGATION_OFF,
417 MMIO_MITIGATION_UCODE_NEEDED,
418 MMIO_MITIGATION_VERW,
419 };
420
421 /* Default mitigation for Processor MMIO Stale Data vulnerabilities */
422 static enum mmio_mitigations mmio_mitigation __ro_after_init = MMIO_MITIGATION_VERW;
423 static bool mmio_nosmt __ro_after_init = false;
424
425 static const char * const mmio_strings[] = {
426 [MMIO_MITIGATION_OFF] = "Vulnerable",
427 [MMIO_MITIGATION_UCODE_NEEDED] = "Vulnerable: Clear CPU buffers attempted, no microcode",
428 [MMIO_MITIGATION_VERW] = "Mitigation: Clear CPU buffers",
429 };
430
mmio_select_mitigation(void)431 static void __init mmio_select_mitigation(void)
432 {
433 u64 ia32_cap;
434
435 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) ||
436 boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN) ||
437 cpu_mitigations_off()) {
438 mmio_mitigation = MMIO_MITIGATION_OFF;
439 return;
440 }
441
442 if (mmio_mitigation == MMIO_MITIGATION_OFF)
443 return;
444
445 ia32_cap = x86_read_arch_cap_msr();
446
447 /*
448 * Enable CPU buffer clear mitigation for host and VMM, if also affected
449 * by MDS or TAA. Otherwise, enable mitigation for VMM only.
450 */
451 if (boot_cpu_has_bug(X86_BUG_MDS) || (boot_cpu_has_bug(X86_BUG_TAA) &&
452 boot_cpu_has(X86_FEATURE_RTM)))
453 static_branch_enable(&mds_user_clear);
454 else
455 static_branch_enable(&mmio_stale_data_clear);
456
457 /*
458 * If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can
459 * be propagated to uncore buffers, clearing the Fill buffers on idle
460 * is required irrespective of SMT state.
461 */
462 if (!(ia32_cap & ARCH_CAP_FBSDP_NO))
463 static_branch_enable(&mds_idle_clear);
464
465 /*
466 * Check if the system has the right microcode.
467 *
468 * CPU Fill buffer clear mitigation is enumerated by either an explicit
469 * FB_CLEAR or by the presence of both MD_CLEAR and L1D_FLUSH on MDS
470 * affected systems.
471 */
472 if ((ia32_cap & ARCH_CAP_FB_CLEAR) ||
473 (boot_cpu_has(X86_FEATURE_MD_CLEAR) &&
474 boot_cpu_has(X86_FEATURE_FLUSH_L1D) &&
475 !(ia32_cap & ARCH_CAP_MDS_NO)))
476 mmio_mitigation = MMIO_MITIGATION_VERW;
477 else
478 mmio_mitigation = MMIO_MITIGATION_UCODE_NEEDED;
479
480 if (mmio_nosmt || cpu_mitigations_auto_nosmt())
481 cpu_smt_disable(false);
482 }
483
mmio_stale_data_parse_cmdline(char * str)484 static int __init mmio_stale_data_parse_cmdline(char *str)
485 {
486 if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
487 return 0;
488
489 if (!str)
490 return -EINVAL;
491
492 if (!strcmp(str, "off")) {
493 mmio_mitigation = MMIO_MITIGATION_OFF;
494 } else if (!strcmp(str, "full")) {
495 mmio_mitigation = MMIO_MITIGATION_VERW;
496 } else if (!strcmp(str, "full,nosmt")) {
497 mmio_mitigation = MMIO_MITIGATION_VERW;
498 mmio_nosmt = true;
499 }
500
501 return 0;
502 }
503 early_param("mmio_stale_data", mmio_stale_data_parse_cmdline);
504
505 #undef pr_fmt
506 #define pr_fmt(fmt) "" fmt
507
md_clear_update_mitigation(void)508 static void __init md_clear_update_mitigation(void)
509 {
510 if (cpu_mitigations_off())
511 return;
512
513 if (!static_key_enabled(&mds_user_clear))
514 goto out;
515
516 /*
517 * mds_user_clear is now enabled. Update MDS, TAA and MMIO Stale Data
518 * mitigation, if necessary.
519 */
520 if (mds_mitigation == MDS_MITIGATION_OFF &&
521 boot_cpu_has_bug(X86_BUG_MDS)) {
522 mds_mitigation = MDS_MITIGATION_FULL;
523 mds_select_mitigation();
524 }
525 if (taa_mitigation == TAA_MITIGATION_OFF &&
526 boot_cpu_has_bug(X86_BUG_TAA)) {
527 taa_mitigation = TAA_MITIGATION_VERW;
528 taa_select_mitigation();
529 }
530 if (mmio_mitigation == MMIO_MITIGATION_OFF &&
531 boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA)) {
532 mmio_mitigation = MMIO_MITIGATION_VERW;
533 mmio_select_mitigation();
534 }
535 out:
536 if (boot_cpu_has_bug(X86_BUG_MDS))
537 pr_info("MDS: %s\n", mds_strings[mds_mitigation]);
538 if (boot_cpu_has_bug(X86_BUG_TAA))
539 pr_info("TAA: %s\n", taa_strings[taa_mitigation]);
540 if (boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
541 pr_info("MMIO Stale Data: %s\n", mmio_strings[mmio_mitigation]);
542 else if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
543 pr_info("MMIO Stale Data: Unknown: No mitigations\n");
544 }
545
md_clear_select_mitigation(void)546 static void __init md_clear_select_mitigation(void)
547 {
548 mds_select_mitigation();
549 taa_select_mitigation();
550 mmio_select_mitigation();
551
552 /*
553 * As MDS, TAA and MMIO Stale Data mitigations are inter-related, update
554 * and print their mitigation after MDS, TAA and MMIO Stale Data
555 * mitigation selection is done.
556 */
557 md_clear_update_mitigation();
558 }
559
560 #undef pr_fmt
561 #define pr_fmt(fmt) "SRBDS: " fmt
562
563 enum srbds_mitigations {
564 SRBDS_MITIGATION_OFF,
565 SRBDS_MITIGATION_UCODE_NEEDED,
566 SRBDS_MITIGATION_FULL,
567 SRBDS_MITIGATION_TSX_OFF,
568 SRBDS_MITIGATION_HYPERVISOR,
569 };
570
571 static enum srbds_mitigations srbds_mitigation __ro_after_init = SRBDS_MITIGATION_FULL;
572
573 static const char * const srbds_strings[] = {
574 [SRBDS_MITIGATION_OFF] = "Vulnerable",
575 [SRBDS_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
576 [SRBDS_MITIGATION_FULL] = "Mitigation: Microcode",
577 [SRBDS_MITIGATION_TSX_OFF] = "Mitigation: TSX disabled",
578 [SRBDS_MITIGATION_HYPERVISOR] = "Unknown: Dependent on hypervisor status",
579 };
580
581 static bool srbds_off;
582
update_srbds_msr(void)583 void update_srbds_msr(void)
584 {
585 u64 mcu_ctrl;
586
587 if (!boot_cpu_has_bug(X86_BUG_SRBDS))
588 return;
589
590 if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
591 return;
592
593 if (srbds_mitigation == SRBDS_MITIGATION_UCODE_NEEDED)
594 return;
595
596 /*
597 * A MDS_NO CPU for which SRBDS mitigation is not needed due to TSX
598 * being disabled and it hasn't received the SRBDS MSR microcode.
599 */
600 if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
601 return;
602
603 rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
604
605 switch (srbds_mitigation) {
606 case SRBDS_MITIGATION_OFF:
607 case SRBDS_MITIGATION_TSX_OFF:
608 mcu_ctrl |= RNGDS_MITG_DIS;
609 break;
610 case SRBDS_MITIGATION_FULL:
611 mcu_ctrl &= ~RNGDS_MITG_DIS;
612 break;
613 default:
614 break;
615 }
616
617 wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
618 }
619
srbds_select_mitigation(void)620 static void __init srbds_select_mitigation(void)
621 {
622 u64 ia32_cap;
623
624 if (!boot_cpu_has_bug(X86_BUG_SRBDS))
625 return;
626
627 /*
628 * Check to see if this is one of the MDS_NO systems supporting TSX that
629 * are only exposed to SRBDS when TSX is enabled or when CPU is affected
630 * by Processor MMIO Stale Data vulnerability.
631 */
632 ia32_cap = x86_read_arch_cap_msr();
633 if ((ia32_cap & ARCH_CAP_MDS_NO) && !boot_cpu_has(X86_FEATURE_RTM) &&
634 !boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
635 srbds_mitigation = SRBDS_MITIGATION_TSX_OFF;
636 else if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
637 srbds_mitigation = SRBDS_MITIGATION_HYPERVISOR;
638 else if (!boot_cpu_has(X86_FEATURE_SRBDS_CTRL))
639 srbds_mitigation = SRBDS_MITIGATION_UCODE_NEEDED;
640 else if (cpu_mitigations_off() || srbds_off)
641 srbds_mitigation = SRBDS_MITIGATION_OFF;
642
643 update_srbds_msr();
644 pr_info("%s\n", srbds_strings[srbds_mitigation]);
645 }
646
srbds_parse_cmdline(char * str)647 static int __init srbds_parse_cmdline(char *str)
648 {
649 if (!str)
650 return -EINVAL;
651
652 if (!boot_cpu_has_bug(X86_BUG_SRBDS))
653 return 0;
654
655 srbds_off = !strcmp(str, "off");
656 return 0;
657 }
658 early_param("srbds", srbds_parse_cmdline);
659
660 #undef pr_fmt
661 #define pr_fmt(fmt) "L1D Flush : " fmt
662
663 enum l1d_flush_mitigations {
664 L1D_FLUSH_OFF = 0,
665 L1D_FLUSH_ON,
666 };
667
668 static enum l1d_flush_mitigations l1d_flush_mitigation __initdata = L1D_FLUSH_OFF;
669
l1d_flush_select_mitigation(void)670 static void __init l1d_flush_select_mitigation(void)
671 {
672 if (!l1d_flush_mitigation || !boot_cpu_has(X86_FEATURE_FLUSH_L1D))
673 return;
674
675 static_branch_enable(&switch_mm_cond_l1d_flush);
676 pr_info("Conditional flush on switch_mm() enabled\n");
677 }
678
l1d_flush_parse_cmdline(char * str)679 static int __init l1d_flush_parse_cmdline(char *str)
680 {
681 if (!strcmp(str, "on"))
682 l1d_flush_mitigation = L1D_FLUSH_ON;
683
684 return 0;
685 }
686 early_param("l1d_flush", l1d_flush_parse_cmdline);
687
688 #undef pr_fmt
689 #define pr_fmt(fmt) "Spectre V1 : " fmt
690
691 enum spectre_v1_mitigation {
692 SPECTRE_V1_MITIGATION_NONE,
693 SPECTRE_V1_MITIGATION_AUTO,
694 };
695
696 static enum spectre_v1_mitigation spectre_v1_mitigation __ro_after_init =
697 SPECTRE_V1_MITIGATION_AUTO;
698
699 static const char * const spectre_v1_strings[] = {
700 [SPECTRE_V1_MITIGATION_NONE] = "Vulnerable: __user pointer sanitization and usercopy barriers only; no swapgs barriers",
701 [SPECTRE_V1_MITIGATION_AUTO] = "Mitigation: usercopy/swapgs barriers and __user pointer sanitization",
702 };
703
704 /*
705 * Does SMAP provide full mitigation against speculative kernel access to
706 * userspace?
707 */
smap_works_speculatively(void)708 static bool smap_works_speculatively(void)
709 {
710 if (!boot_cpu_has(X86_FEATURE_SMAP))
711 return false;
712
713 /*
714 * On CPUs which are vulnerable to Meltdown, SMAP does not
715 * prevent speculative access to user data in the L1 cache.
716 * Consider SMAP to be non-functional as a mitigation on these
717 * CPUs.
718 */
719 if (boot_cpu_has(X86_BUG_CPU_MELTDOWN))
720 return false;
721
722 return true;
723 }
724
spectre_v1_select_mitigation(void)725 static void __init spectre_v1_select_mitigation(void)
726 {
727 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1) || cpu_mitigations_off()) {
728 spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE;
729 return;
730 }
731
732 if (spectre_v1_mitigation == SPECTRE_V1_MITIGATION_AUTO) {
733 /*
734 * With Spectre v1, a user can speculatively control either
735 * path of a conditional swapgs with a user-controlled GS
736 * value. The mitigation is to add lfences to both code paths.
737 *
738 * If FSGSBASE is enabled, the user can put a kernel address in
739 * GS, in which case SMAP provides no protection.
740 *
741 * If FSGSBASE is disabled, the user can only put a user space
742 * address in GS. That makes an attack harder, but still
743 * possible if there's no SMAP protection.
744 */
745 if (boot_cpu_has(X86_FEATURE_FSGSBASE) ||
746 !smap_works_speculatively()) {
747 /*
748 * Mitigation can be provided from SWAPGS itself or
749 * PTI as the CR3 write in the Meltdown mitigation
750 * is serializing.
751 *
752 * If neither is there, mitigate with an LFENCE to
753 * stop speculation through swapgs.
754 */
755 if (boot_cpu_has_bug(X86_BUG_SWAPGS) &&
756 !boot_cpu_has(X86_FEATURE_PTI))
757 setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_USER);
758
759 /*
760 * Enable lfences in the kernel entry (non-swapgs)
761 * paths, to prevent user entry from speculatively
762 * skipping swapgs.
763 */
764 setup_force_cpu_cap(X86_FEATURE_FENCE_SWAPGS_KERNEL);
765 }
766 }
767
768 pr_info("%s\n", spectre_v1_strings[spectre_v1_mitigation]);
769 }
770
nospectre_v1_cmdline(char * str)771 static int __init nospectre_v1_cmdline(char *str)
772 {
773 spectre_v1_mitigation = SPECTRE_V1_MITIGATION_NONE;
774 return 0;
775 }
776 early_param("nospectre_v1", nospectre_v1_cmdline);
777
778 static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
779 SPECTRE_V2_NONE;
780
781 #undef pr_fmt
782 #define pr_fmt(fmt) "RETBleed: " fmt
783
784 enum retbleed_mitigation {
785 RETBLEED_MITIGATION_NONE,
786 RETBLEED_MITIGATION_UNRET,
787 RETBLEED_MITIGATION_IBPB,
788 RETBLEED_MITIGATION_IBRS,
789 RETBLEED_MITIGATION_EIBRS,
790 };
791
792 enum retbleed_mitigation_cmd {
793 RETBLEED_CMD_OFF,
794 RETBLEED_CMD_AUTO,
795 RETBLEED_CMD_UNRET,
796 RETBLEED_CMD_IBPB,
797 };
798
799 static const char * const retbleed_strings[] = {
800 [RETBLEED_MITIGATION_NONE] = "Vulnerable",
801 [RETBLEED_MITIGATION_UNRET] = "Mitigation: untrained return thunk",
802 [RETBLEED_MITIGATION_IBPB] = "Mitigation: IBPB",
803 [RETBLEED_MITIGATION_IBRS] = "Mitigation: IBRS",
804 [RETBLEED_MITIGATION_EIBRS] = "Mitigation: Enhanced IBRS",
805 };
806
807 static enum retbleed_mitigation retbleed_mitigation __ro_after_init =
808 RETBLEED_MITIGATION_NONE;
809 static enum retbleed_mitigation_cmd retbleed_cmd __ro_after_init =
810 RETBLEED_CMD_AUTO;
811
812 static int __ro_after_init retbleed_nosmt = false;
813
retbleed_parse_cmdline(char * str)814 static int __init retbleed_parse_cmdline(char *str)
815 {
816 if (!str)
817 return -EINVAL;
818
819 while (str) {
820 char *next = strchr(str, ',');
821 if (next) {
822 *next = 0;
823 next++;
824 }
825
826 if (!strcmp(str, "off")) {
827 retbleed_cmd = RETBLEED_CMD_OFF;
828 } else if (!strcmp(str, "auto")) {
829 retbleed_cmd = RETBLEED_CMD_AUTO;
830 } else if (!strcmp(str, "unret")) {
831 retbleed_cmd = RETBLEED_CMD_UNRET;
832 } else if (!strcmp(str, "ibpb")) {
833 retbleed_cmd = RETBLEED_CMD_IBPB;
834 } else if (!strcmp(str, "nosmt")) {
835 retbleed_nosmt = true;
836 } else {
837 pr_err("Ignoring unknown retbleed option (%s).", str);
838 }
839
840 str = next;
841 }
842
843 return 0;
844 }
845 early_param("retbleed", retbleed_parse_cmdline);
846
847 #define RETBLEED_UNTRAIN_MSG "WARNING: BTB untrained return thunk mitigation is only effective on AMD/Hygon!\n"
848 #define RETBLEED_INTEL_MSG "WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible!\n"
849
retbleed_select_mitigation(void)850 static void __init retbleed_select_mitigation(void)
851 {
852 bool mitigate_smt = false;
853
854 if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off())
855 return;
856
857 switch (retbleed_cmd) {
858 case RETBLEED_CMD_OFF:
859 return;
860
861 case RETBLEED_CMD_UNRET:
862 if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY)) {
863 retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
864 } else {
865 pr_err("WARNING: kernel not compiled with CPU_UNRET_ENTRY.\n");
866 goto do_cmd_auto;
867 }
868 break;
869
870 case RETBLEED_CMD_IBPB:
871 if (!boot_cpu_has(X86_FEATURE_IBPB)) {
872 pr_err("WARNING: CPU does not support IBPB.\n");
873 goto do_cmd_auto;
874 } else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) {
875 retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
876 } else {
877 pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
878 goto do_cmd_auto;
879 }
880 break;
881
882 do_cmd_auto:
883 case RETBLEED_CMD_AUTO:
884 default:
885 if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
886 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
887 if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
888 retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
889 else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY) && boot_cpu_has(X86_FEATURE_IBPB))
890 retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
891 }
892
893 /*
894 * The Intel mitigation (IBRS or eIBRS) was already selected in
895 * spectre_v2_select_mitigation(). 'retbleed_mitigation' will
896 * be set accordingly below.
897 */
898
899 break;
900 }
901
902 switch (retbleed_mitigation) {
903 case RETBLEED_MITIGATION_UNRET:
904 setup_force_cpu_cap(X86_FEATURE_RETHUNK);
905 setup_force_cpu_cap(X86_FEATURE_UNRET);
906
907 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
908 boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
909 pr_err(RETBLEED_UNTRAIN_MSG);
910
911 mitigate_smt = true;
912 break;
913
914 case RETBLEED_MITIGATION_IBPB:
915 setup_force_cpu_cap(X86_FEATURE_ENTRY_IBPB);
916 mitigate_smt = true;
917 break;
918
919 default:
920 break;
921 }
922
923 if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) &&
924 (retbleed_nosmt || cpu_mitigations_auto_nosmt()))
925 cpu_smt_disable(false);
926
927 /*
928 * Let IBRS trump all on Intel without affecting the effects of the
929 * retbleed= cmdline option.
930 */
931 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
932 switch (spectre_v2_enabled) {
933 case SPECTRE_V2_IBRS:
934 retbleed_mitigation = RETBLEED_MITIGATION_IBRS;
935 break;
936 case SPECTRE_V2_EIBRS:
937 case SPECTRE_V2_EIBRS_RETPOLINE:
938 case SPECTRE_V2_EIBRS_LFENCE:
939 retbleed_mitigation = RETBLEED_MITIGATION_EIBRS;
940 break;
941 default:
942 pr_err(RETBLEED_INTEL_MSG);
943 }
944 }
945
946 pr_info("%s\n", retbleed_strings[retbleed_mitigation]);
947 }
948
949 #undef pr_fmt
950 #define pr_fmt(fmt) "Spectre V2 : " fmt
951
952 static enum spectre_v2_user_mitigation spectre_v2_user_stibp __ro_after_init =
953 SPECTRE_V2_USER_NONE;
954 static enum spectre_v2_user_mitigation spectre_v2_user_ibpb __ro_after_init =
955 SPECTRE_V2_USER_NONE;
956
957 #ifdef CONFIG_RETPOLINE
958 static bool spectre_v2_bad_module;
959
retpoline_module_ok(bool has_retpoline)960 bool retpoline_module_ok(bool has_retpoline)
961 {
962 if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
963 return true;
964
965 pr_err("System may be vulnerable to spectre v2\n");
966 spectre_v2_bad_module = true;
967 return false;
968 }
969
spectre_v2_module_string(void)970 static inline const char *spectre_v2_module_string(void)
971 {
972 return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
973 }
974 #else
spectre_v2_module_string(void)975 static inline const char *spectre_v2_module_string(void) { return ""; }
976 #endif
977
978 #define SPECTRE_V2_LFENCE_MSG "WARNING: LFENCE mitigation is not recommended for this CPU, data leaks possible!\n"
979 #define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n"
980 #define SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS+LFENCE mitigation and SMT, data leaks possible via Spectre v2 BHB attacks!\n"
981 #define SPECTRE_V2_IBRS_PERF_MSG "WARNING: IBRS mitigation selected on Enhanced IBRS CPU, this may cause unnecessary performance loss\n"
982
983 #ifdef CONFIG_BPF_SYSCALL
unpriv_ebpf_notify(int new_state)984 void unpriv_ebpf_notify(int new_state)
985 {
986 if (new_state)
987 return;
988
989 /* Unprivileged eBPF is enabled */
990
991 switch (spectre_v2_enabled) {
992 case SPECTRE_V2_EIBRS:
993 pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
994 break;
995 case SPECTRE_V2_EIBRS_LFENCE:
996 if (sched_smt_active())
997 pr_err(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
998 break;
999 default:
1000 break;
1001 }
1002 }
1003 #endif
1004
match_option(const char * arg,int arglen,const char * opt)1005 static inline bool match_option(const char *arg, int arglen, const char *opt)
1006 {
1007 int len = strlen(opt);
1008
1009 return len == arglen && !strncmp(arg, opt, len);
1010 }
1011
1012 /* The kernel command line selection for spectre v2 */
1013 enum spectre_v2_mitigation_cmd {
1014 SPECTRE_V2_CMD_NONE,
1015 SPECTRE_V2_CMD_AUTO,
1016 SPECTRE_V2_CMD_FORCE,
1017 SPECTRE_V2_CMD_RETPOLINE,
1018 SPECTRE_V2_CMD_RETPOLINE_GENERIC,
1019 SPECTRE_V2_CMD_RETPOLINE_LFENCE,
1020 SPECTRE_V2_CMD_EIBRS,
1021 SPECTRE_V2_CMD_EIBRS_RETPOLINE,
1022 SPECTRE_V2_CMD_EIBRS_LFENCE,
1023 SPECTRE_V2_CMD_IBRS,
1024 };
1025
1026 enum spectre_v2_user_cmd {
1027 SPECTRE_V2_USER_CMD_NONE,
1028 SPECTRE_V2_USER_CMD_AUTO,
1029 SPECTRE_V2_USER_CMD_FORCE,
1030 SPECTRE_V2_USER_CMD_PRCTL,
1031 SPECTRE_V2_USER_CMD_PRCTL_IBPB,
1032 SPECTRE_V2_USER_CMD_SECCOMP,
1033 SPECTRE_V2_USER_CMD_SECCOMP_IBPB,
1034 };
1035
1036 static const char * const spectre_v2_user_strings[] = {
1037 [SPECTRE_V2_USER_NONE] = "User space: Vulnerable",
1038 [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection",
1039 [SPECTRE_V2_USER_STRICT_PREFERRED] = "User space: Mitigation: STIBP always-on protection",
1040 [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl",
1041 [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl",
1042 };
1043
1044 static const struct {
1045 const char *option;
1046 enum spectre_v2_user_cmd cmd;
1047 bool secure;
1048 } v2_user_options[] __initconst = {
1049 { "auto", SPECTRE_V2_USER_CMD_AUTO, false },
1050 { "off", SPECTRE_V2_USER_CMD_NONE, false },
1051 { "on", SPECTRE_V2_USER_CMD_FORCE, true },
1052 { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false },
1053 { "prctl,ibpb", SPECTRE_V2_USER_CMD_PRCTL_IBPB, false },
1054 { "seccomp", SPECTRE_V2_USER_CMD_SECCOMP, false },
1055 { "seccomp,ibpb", SPECTRE_V2_USER_CMD_SECCOMP_IBPB, false },
1056 };
1057
spec_v2_user_print_cond(const char * reason,bool secure)1058 static void __init spec_v2_user_print_cond(const char *reason, bool secure)
1059 {
1060 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
1061 pr_info("spectre_v2_user=%s forced on command line.\n", reason);
1062 }
1063
1064 static __ro_after_init enum spectre_v2_mitigation_cmd spectre_v2_cmd;
1065
1066 static enum spectre_v2_user_cmd __init
spectre_v2_parse_user_cmdline(void)1067 spectre_v2_parse_user_cmdline(void)
1068 {
1069 char arg[20];
1070 int ret, i;
1071
1072 switch (spectre_v2_cmd) {
1073 case SPECTRE_V2_CMD_NONE:
1074 return SPECTRE_V2_USER_CMD_NONE;
1075 case SPECTRE_V2_CMD_FORCE:
1076 return SPECTRE_V2_USER_CMD_FORCE;
1077 default:
1078 break;
1079 }
1080
1081 ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
1082 arg, sizeof(arg));
1083 if (ret < 0)
1084 return SPECTRE_V2_USER_CMD_AUTO;
1085
1086 for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
1087 if (match_option(arg, ret, v2_user_options[i].option)) {
1088 spec_v2_user_print_cond(v2_user_options[i].option,
1089 v2_user_options[i].secure);
1090 return v2_user_options[i].cmd;
1091 }
1092 }
1093
1094 pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg);
1095 return SPECTRE_V2_USER_CMD_AUTO;
1096 }
1097
spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)1098 static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)
1099 {
1100 return mode == SPECTRE_V2_IBRS ||
1101 mode == SPECTRE_V2_EIBRS ||
1102 mode == SPECTRE_V2_EIBRS_RETPOLINE ||
1103 mode == SPECTRE_V2_EIBRS_LFENCE;
1104 }
1105
1106 static void __init
spectre_v2_user_select_mitigation(void)1107 spectre_v2_user_select_mitigation(void)
1108 {
1109 enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE;
1110 bool smt_possible = IS_ENABLED(CONFIG_SMP);
1111 enum spectre_v2_user_cmd cmd;
1112
1113 if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
1114 return;
1115
1116 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
1117 cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
1118 smt_possible = false;
1119
1120 cmd = spectre_v2_parse_user_cmdline();
1121 switch (cmd) {
1122 case SPECTRE_V2_USER_CMD_NONE:
1123 goto set_mode;
1124 case SPECTRE_V2_USER_CMD_FORCE:
1125 mode = SPECTRE_V2_USER_STRICT;
1126 break;
1127 case SPECTRE_V2_USER_CMD_AUTO:
1128 case SPECTRE_V2_USER_CMD_PRCTL:
1129 case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
1130 mode = SPECTRE_V2_USER_PRCTL;
1131 break;
1132 case SPECTRE_V2_USER_CMD_SECCOMP:
1133 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
1134 if (IS_ENABLED(CONFIG_SECCOMP))
1135 mode = SPECTRE_V2_USER_SECCOMP;
1136 else
1137 mode = SPECTRE_V2_USER_PRCTL;
1138 break;
1139 }
1140
1141 /* Initialize Indirect Branch Prediction Barrier */
1142 if (boot_cpu_has(X86_FEATURE_IBPB)) {
1143 setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
1144
1145 spectre_v2_user_ibpb = mode;
1146 switch (cmd) {
1147 case SPECTRE_V2_USER_CMD_FORCE:
1148 case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
1149 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
1150 static_branch_enable(&switch_mm_always_ibpb);
1151 spectre_v2_user_ibpb = SPECTRE_V2_USER_STRICT;
1152 break;
1153 case SPECTRE_V2_USER_CMD_PRCTL:
1154 case SPECTRE_V2_USER_CMD_AUTO:
1155 case SPECTRE_V2_USER_CMD_SECCOMP:
1156 static_branch_enable(&switch_mm_cond_ibpb);
1157 break;
1158 default:
1159 break;
1160 }
1161
1162 pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
1163 static_key_enabled(&switch_mm_always_ibpb) ?
1164 "always-on" : "conditional");
1165 }
1166
1167 /*
1168 * If no STIBP, IBRS or enhanced IBRS is enabled, or SMT impossible,
1169 * STIBP is not required.
1170 */
1171 if (!boot_cpu_has(X86_FEATURE_STIBP) ||
1172 !smt_possible ||
1173 spectre_v2_in_ibrs_mode(spectre_v2_enabled))
1174 return;
1175
1176 /*
1177 * At this point, an STIBP mode other than "off" has been set.
1178 * If STIBP support is not being forced, check if STIBP always-on
1179 * is preferred.
1180 */
1181 if (mode != SPECTRE_V2_USER_STRICT &&
1182 boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
1183 mode = SPECTRE_V2_USER_STRICT_PREFERRED;
1184
1185 if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET ||
1186 retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
1187 if (mode != SPECTRE_V2_USER_STRICT &&
1188 mode != SPECTRE_V2_USER_STRICT_PREFERRED)
1189 pr_info("Selecting STIBP always-on mode to complement retbleed mitigation\n");
1190 mode = SPECTRE_V2_USER_STRICT_PREFERRED;
1191 }
1192
1193 spectre_v2_user_stibp = mode;
1194
1195 set_mode:
1196 pr_info("%s\n", spectre_v2_user_strings[mode]);
1197 }
1198
1199 static const char * const spectre_v2_strings[] = {
1200 [SPECTRE_V2_NONE] = "Vulnerable",
1201 [SPECTRE_V2_RETPOLINE] = "Mitigation: Retpolines",
1202 [SPECTRE_V2_LFENCE] = "Mitigation: LFENCE",
1203 [SPECTRE_V2_EIBRS] = "Mitigation: Enhanced IBRS",
1204 [SPECTRE_V2_EIBRS_LFENCE] = "Mitigation: Enhanced IBRS + LFENCE",
1205 [SPECTRE_V2_EIBRS_RETPOLINE] = "Mitigation: Enhanced IBRS + Retpolines",
1206 [SPECTRE_V2_IBRS] = "Mitigation: IBRS",
1207 };
1208
1209 static const struct {
1210 const char *option;
1211 enum spectre_v2_mitigation_cmd cmd;
1212 bool secure;
1213 } mitigation_options[] __initconst = {
1214 { "off", SPECTRE_V2_CMD_NONE, false },
1215 { "on", SPECTRE_V2_CMD_FORCE, true },
1216 { "retpoline", SPECTRE_V2_CMD_RETPOLINE, false },
1217 { "retpoline,amd", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false },
1218 { "retpoline,lfence", SPECTRE_V2_CMD_RETPOLINE_LFENCE, false },
1219 { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
1220 { "eibrs", SPECTRE_V2_CMD_EIBRS, false },
1221 { "eibrs,lfence", SPECTRE_V2_CMD_EIBRS_LFENCE, false },
1222 { "eibrs,retpoline", SPECTRE_V2_CMD_EIBRS_RETPOLINE, false },
1223 { "auto", SPECTRE_V2_CMD_AUTO, false },
1224 { "ibrs", SPECTRE_V2_CMD_IBRS, false },
1225 };
1226
spec_v2_print_cond(const char * reason,bool secure)1227 static void __init spec_v2_print_cond(const char *reason, bool secure)
1228 {
1229 if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
1230 pr_info("%s selected on command line.\n", reason);
1231 }
1232
spectre_v2_parse_cmdline(void)1233 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
1234 {
1235 enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
1236 char arg[20];
1237 int ret, i;
1238
1239 if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||
1240 cpu_mitigations_off())
1241 return SPECTRE_V2_CMD_NONE;
1242
1243 ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
1244 if (ret < 0)
1245 return SPECTRE_V2_CMD_AUTO;
1246
1247 for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
1248 if (!match_option(arg, ret, mitigation_options[i].option))
1249 continue;
1250 cmd = mitigation_options[i].cmd;
1251 break;
1252 }
1253
1254 if (i >= ARRAY_SIZE(mitigation_options)) {
1255 pr_err("unknown option (%s). Switching to AUTO select\n", arg);
1256 return SPECTRE_V2_CMD_AUTO;
1257 }
1258
1259 if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
1260 cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
1261 cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC ||
1262 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
1263 cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
1264 !IS_ENABLED(CONFIG_RETPOLINE)) {
1265 pr_err("%s selected but not compiled in. Switching to AUTO select\n",
1266 mitigation_options[i].option);
1267 return SPECTRE_V2_CMD_AUTO;
1268 }
1269
1270 if ((cmd == SPECTRE_V2_CMD_EIBRS ||
1271 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
1272 cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
1273 !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
1274 pr_err("%s selected but CPU doesn't have eIBRS. Switching to AUTO select\n",
1275 mitigation_options[i].option);
1276 return SPECTRE_V2_CMD_AUTO;
1277 }
1278
1279 if ((cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
1280 cmd == SPECTRE_V2_CMD_EIBRS_LFENCE) &&
1281 !boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
1282 pr_err("%s selected, but CPU doesn't have a serializing LFENCE. Switching to AUTO select\n",
1283 mitigation_options[i].option);
1284 return SPECTRE_V2_CMD_AUTO;
1285 }
1286
1287 if (cmd == SPECTRE_V2_CMD_IBRS && !IS_ENABLED(CONFIG_CPU_IBRS_ENTRY)) {
1288 pr_err("%s selected but not compiled in. Switching to AUTO select\n",
1289 mitigation_options[i].option);
1290 return SPECTRE_V2_CMD_AUTO;
1291 }
1292
1293 if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
1294 pr_err("%s selected but not Intel CPU. Switching to AUTO select\n",
1295 mitigation_options[i].option);
1296 return SPECTRE_V2_CMD_AUTO;
1297 }
1298
1299 if (cmd == SPECTRE_V2_CMD_IBRS && !boot_cpu_has(X86_FEATURE_IBRS)) {
1300 pr_err("%s selected but CPU doesn't have IBRS. Switching to AUTO select\n",
1301 mitigation_options[i].option);
1302 return SPECTRE_V2_CMD_AUTO;
1303 }
1304
1305 if (cmd == SPECTRE_V2_CMD_IBRS && boot_cpu_has(X86_FEATURE_XENPV)) {
1306 pr_err("%s selected but running as XenPV guest. Switching to AUTO select\n",
1307 mitigation_options[i].option);
1308 return SPECTRE_V2_CMD_AUTO;
1309 }
1310
1311 spec_v2_print_cond(mitigation_options[i].option,
1312 mitigation_options[i].secure);
1313 return cmd;
1314 }
1315
spectre_v2_select_retpoline(void)1316 static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void)
1317 {
1318 if (!IS_ENABLED(CONFIG_RETPOLINE)) {
1319 pr_err("Kernel not compiled with retpoline; no mitigation available!");
1320 return SPECTRE_V2_NONE;
1321 }
1322
1323 return SPECTRE_V2_RETPOLINE;
1324 }
1325
1326 /* Disable in-kernel use of non-RSB RET predictors */
spec_ctrl_disable_kernel_rrsba(void)1327 static void __init spec_ctrl_disable_kernel_rrsba(void)
1328 {
1329 u64 ia32_cap;
1330
1331 if (!boot_cpu_has(X86_FEATURE_RRSBA_CTRL))
1332 return;
1333
1334 ia32_cap = x86_read_arch_cap_msr();
1335
1336 if (ia32_cap & ARCH_CAP_RRSBA) {
1337 x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S;
1338 write_spec_ctrl_current(x86_spec_ctrl_base, true);
1339 }
1340 }
1341
spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_mitigation mode)1342 static void __init spectre_v2_determine_rsb_fill_type_at_vmexit(enum spectre_v2_mitigation mode)
1343 {
1344 /*
1345 * Similar to context switches, there are two types of RSB attacks
1346 * after VM exit:
1347 *
1348 * 1) RSB underflow
1349 *
1350 * 2) Poisoned RSB entry
1351 *
1352 * When retpoline is enabled, both are mitigated by filling/clearing
1353 * the RSB.
1354 *
1355 * When IBRS is enabled, while #1 would be mitigated by the IBRS branch
1356 * prediction isolation protections, RSB still needs to be cleared
1357 * because of #2. Note that SMEP provides no protection here, unlike
1358 * user-space-poisoned RSB entries.
1359 *
1360 * eIBRS should protect against RSB poisoning, but if the EIBRS_PBRSB
1361 * bug is present then a LITE version of RSB protection is required,
1362 * just a single call needs to retire before a RET is executed.
1363 */
1364 switch (mode) {
1365 case SPECTRE_V2_NONE:
1366 return;
1367
1368 case SPECTRE_V2_EIBRS_LFENCE:
1369 case SPECTRE_V2_EIBRS:
1370 if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) {
1371 setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT_LITE);
1372 pr_info("Spectre v2 / PBRSB-eIBRS: Retire a single CALL on VMEXIT\n");
1373 }
1374 return;
1375
1376 case SPECTRE_V2_EIBRS_RETPOLINE:
1377 case SPECTRE_V2_RETPOLINE:
1378 case SPECTRE_V2_LFENCE:
1379 case SPECTRE_V2_IBRS:
1380 setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT);
1381 pr_info("Spectre v2 / SpectreRSB : Filling RSB on VMEXIT\n");
1382 return;
1383 }
1384
1385 pr_warn_once("Unknown Spectre v2 mode, disabling RSB mitigation at VM exit");
1386 dump_stack();
1387 }
1388
spectre_v2_select_mitigation(void)1389 static void __init spectre_v2_select_mitigation(void)
1390 {
1391 enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
1392 enum spectre_v2_mitigation mode = SPECTRE_V2_NONE;
1393
1394 /*
1395 * If the CPU is not affected and the command line mode is NONE or AUTO
1396 * then nothing to do.
1397 */
1398 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
1399 (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO))
1400 return;
1401
1402 switch (cmd) {
1403 case SPECTRE_V2_CMD_NONE:
1404 return;
1405
1406 case SPECTRE_V2_CMD_FORCE:
1407 case SPECTRE_V2_CMD_AUTO:
1408 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
1409 mode = SPECTRE_V2_EIBRS;
1410 break;
1411 }
1412
1413 if (IS_ENABLED(CONFIG_CPU_IBRS_ENTRY) &&
1414 boot_cpu_has_bug(X86_BUG_RETBLEED) &&
1415 retbleed_cmd != RETBLEED_CMD_OFF &&
1416 boot_cpu_has(X86_FEATURE_IBRS) &&
1417 boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
1418 mode = SPECTRE_V2_IBRS;
1419 break;
1420 }
1421
1422 mode = spectre_v2_select_retpoline();
1423 break;
1424
1425 case SPECTRE_V2_CMD_RETPOLINE_LFENCE:
1426 pr_err(SPECTRE_V2_LFENCE_MSG);
1427 mode = SPECTRE_V2_LFENCE;
1428 break;
1429
1430 case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
1431 mode = SPECTRE_V2_RETPOLINE;
1432 break;
1433
1434 case SPECTRE_V2_CMD_RETPOLINE:
1435 mode = spectre_v2_select_retpoline();
1436 break;
1437
1438 case SPECTRE_V2_CMD_IBRS:
1439 mode = SPECTRE_V2_IBRS;
1440 break;
1441
1442 case SPECTRE_V2_CMD_EIBRS:
1443 mode = SPECTRE_V2_EIBRS;
1444 break;
1445
1446 case SPECTRE_V2_CMD_EIBRS_LFENCE:
1447 mode = SPECTRE_V2_EIBRS_LFENCE;
1448 break;
1449
1450 case SPECTRE_V2_CMD_EIBRS_RETPOLINE:
1451 mode = SPECTRE_V2_EIBRS_RETPOLINE;
1452 break;
1453 }
1454
1455 if (mode == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
1456 pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);
1457
1458 if (spectre_v2_in_ibrs_mode(mode)) {
1459 x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
1460 write_spec_ctrl_current(x86_spec_ctrl_base, true);
1461 }
1462
1463 switch (mode) {
1464 case SPECTRE_V2_NONE:
1465 case SPECTRE_V2_EIBRS:
1466 break;
1467
1468 case SPECTRE_V2_IBRS:
1469 setup_force_cpu_cap(X86_FEATURE_KERNEL_IBRS);
1470 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED))
1471 pr_warn(SPECTRE_V2_IBRS_PERF_MSG);
1472 break;
1473
1474 case SPECTRE_V2_LFENCE:
1475 case SPECTRE_V2_EIBRS_LFENCE:
1476 setup_force_cpu_cap(X86_FEATURE_RETPOLINE_LFENCE);
1477 fallthrough;
1478
1479 case SPECTRE_V2_RETPOLINE:
1480 case SPECTRE_V2_EIBRS_RETPOLINE:
1481 setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
1482 break;
1483 }
1484
1485 /*
1486 * Disable alternate RSB predictions in kernel when indirect CALLs and
1487 * JMPs gets protection against BHI and Intramode-BTI, but RET
1488 * prediction from a non-RSB predictor is still a risk.
1489 */
1490 if (mode == SPECTRE_V2_EIBRS_LFENCE ||
1491 mode == SPECTRE_V2_EIBRS_RETPOLINE ||
1492 mode == SPECTRE_V2_RETPOLINE)
1493 spec_ctrl_disable_kernel_rrsba();
1494
1495 spectre_v2_enabled = mode;
1496 pr_info("%s\n", spectre_v2_strings[mode]);
1497
1498 /*
1499 * If Spectre v2 protection has been enabled, fill the RSB during a
1500 * context switch. In general there are two types of RSB attacks
1501 * across context switches, for which the CALLs/RETs may be unbalanced.
1502 *
1503 * 1) RSB underflow
1504 *
1505 * Some Intel parts have "bottomless RSB". When the RSB is empty,
1506 * speculated return targets may come from the branch predictor,
1507 * which could have a user-poisoned BTB or BHB entry.
1508 *
1509 * AMD has it even worse: *all* returns are speculated from the BTB,
1510 * regardless of the state of the RSB.
1511 *
1512 * When IBRS or eIBRS is enabled, the "user -> kernel" attack
1513 * scenario is mitigated by the IBRS branch prediction isolation
1514 * properties, so the RSB buffer filling wouldn't be necessary to
1515 * protect against this type of attack.
1516 *
1517 * The "user -> user" attack scenario is mitigated by RSB filling.
1518 *
1519 * 2) Poisoned RSB entry
1520 *
1521 * If the 'next' in-kernel return stack is shorter than 'prev',
1522 * 'next' could be tricked into speculating with a user-poisoned RSB
1523 * entry.
1524 *
1525 * The "user -> kernel" attack scenario is mitigated by SMEP and
1526 * eIBRS.
1527 *
1528 * The "user -> user" scenario, also known as SpectreBHB, requires
1529 * RSB clearing.
1530 *
1531 * So to mitigate all cases, unconditionally fill RSB on context
1532 * switches.
1533 *
1534 * FIXME: Is this pointless for retbleed-affected AMD?
1535 */
1536 setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
1537 pr_info("Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch\n");
1538
1539 spectre_v2_determine_rsb_fill_type_at_vmexit(mode);
1540
1541 /*
1542 * Retpoline protects the kernel, but doesn't protect firmware. IBRS
1543 * and Enhanced IBRS protect firmware too, so enable IBRS around
1544 * firmware calls only when IBRS / Enhanced IBRS aren't otherwise
1545 * enabled.
1546 *
1547 * Use "mode" to check Enhanced IBRS instead of boot_cpu_has(), because
1548 * the user might select retpoline on the kernel command line and if
1549 * the CPU supports Enhanced IBRS, kernel might un-intentionally not
1550 * enable IBRS around firmware calls.
1551 */
1552 if (boot_cpu_has_bug(X86_BUG_RETBLEED) &&
1553 boot_cpu_has(X86_FEATURE_IBPB) &&
1554 (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
1555 boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) {
1556
1557 if (retbleed_cmd != RETBLEED_CMD_IBPB) {
1558 setup_force_cpu_cap(X86_FEATURE_USE_IBPB_FW);
1559 pr_info("Enabling Speculation Barrier for firmware calls\n");
1560 }
1561
1562 } else if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) {
1563 setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
1564 pr_info("Enabling Restricted Speculation for firmware calls\n");
1565 }
1566
1567 /* Set up IBPB and STIBP depending on the general spectre V2 command */
1568 spectre_v2_cmd = cmd;
1569 }
1570
update_stibp_msr(void * __unused)1571 static void update_stibp_msr(void * __unused)
1572 {
1573 u64 val = spec_ctrl_current() | (x86_spec_ctrl_base & SPEC_CTRL_STIBP);
1574 write_spec_ctrl_current(val, true);
1575 }
1576
1577 /* Update x86_spec_ctrl_base in case SMT state changed. */
update_stibp_strict(void)1578 static void update_stibp_strict(void)
1579 {
1580 u64 mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP;
1581
1582 if (sched_smt_active())
1583 mask |= SPEC_CTRL_STIBP;
1584
1585 if (mask == x86_spec_ctrl_base)
1586 return;
1587
1588 pr_info("Update user space SMT mitigation: STIBP %s\n",
1589 mask & SPEC_CTRL_STIBP ? "always-on" : "off");
1590 x86_spec_ctrl_base = mask;
1591 on_each_cpu(update_stibp_msr, NULL, 1);
1592 }
1593
1594 /* Update the static key controlling the evaluation of TIF_SPEC_IB */
update_indir_branch_cond(void)1595 static void update_indir_branch_cond(void)
1596 {
1597 if (sched_smt_active())
1598 static_branch_enable(&switch_to_cond_stibp);
1599 else
1600 static_branch_disable(&switch_to_cond_stibp);
1601 }
1602
1603 #undef pr_fmt
1604 #define pr_fmt(fmt) fmt
1605
1606 /* Update the static key controlling the MDS CPU buffer clear in idle */
update_mds_branch_idle(void)1607 static void update_mds_branch_idle(void)
1608 {
1609 u64 ia32_cap = x86_read_arch_cap_msr();
1610
1611 /*
1612 * Enable the idle clearing if SMT is active on CPUs which are
1613 * affected only by MSBDS and not any other MDS variant.
1614 *
1615 * The other variants cannot be mitigated when SMT is enabled, so
1616 * clearing the buffers on idle just to prevent the Store Buffer
1617 * repartitioning leak would be a window dressing exercise.
1618 */
1619 if (!boot_cpu_has_bug(X86_BUG_MSBDS_ONLY))
1620 return;
1621
1622 if (sched_smt_active()) {
1623 static_branch_enable(&mds_idle_clear);
1624 } else if (mmio_mitigation == MMIO_MITIGATION_OFF ||
1625 (ia32_cap & ARCH_CAP_FBSDP_NO)) {
1626 static_branch_disable(&mds_idle_clear);
1627 }
1628 }
1629
1630 #define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
1631 #define TAA_MSG_SMT "TAA CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/tsx_async_abort.html for more details.\n"
1632 #define MMIO_MSG_SMT "MMIO Stale Data CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/processor_mmio_stale_data.html for more details.\n"
1633
cpu_bugs_smt_update(void)1634 void cpu_bugs_smt_update(void)
1635 {
1636 mutex_lock(&spec_ctrl_mutex);
1637
1638 if (sched_smt_active() && unprivileged_ebpf_enabled() &&
1639 spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
1640 pr_warn_once(SPECTRE_V2_EIBRS_LFENCE_EBPF_SMT_MSG);
1641
1642 switch (spectre_v2_user_stibp) {
1643 case SPECTRE_V2_USER_NONE:
1644 break;
1645 case SPECTRE_V2_USER_STRICT:
1646 case SPECTRE_V2_USER_STRICT_PREFERRED:
1647 update_stibp_strict();
1648 break;
1649 case SPECTRE_V2_USER_PRCTL:
1650 case SPECTRE_V2_USER_SECCOMP:
1651 update_indir_branch_cond();
1652 break;
1653 }
1654
1655 switch (mds_mitigation) {
1656 case MDS_MITIGATION_FULL:
1657 case MDS_MITIGATION_VMWERV:
1658 if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
1659 pr_warn_once(MDS_MSG_SMT);
1660 update_mds_branch_idle();
1661 break;
1662 case MDS_MITIGATION_OFF:
1663 break;
1664 }
1665
1666 switch (taa_mitigation) {
1667 case TAA_MITIGATION_VERW:
1668 case TAA_MITIGATION_UCODE_NEEDED:
1669 if (sched_smt_active())
1670 pr_warn_once(TAA_MSG_SMT);
1671 break;
1672 case TAA_MITIGATION_TSX_DISABLED:
1673 case TAA_MITIGATION_OFF:
1674 break;
1675 }
1676
1677 switch (mmio_mitigation) {
1678 case MMIO_MITIGATION_VERW:
1679 case MMIO_MITIGATION_UCODE_NEEDED:
1680 if (sched_smt_active())
1681 pr_warn_once(MMIO_MSG_SMT);
1682 break;
1683 case MMIO_MITIGATION_OFF:
1684 break;
1685 }
1686
1687 mutex_unlock(&spec_ctrl_mutex);
1688 }
1689
1690 #undef pr_fmt
1691 #define pr_fmt(fmt) "Speculative Store Bypass: " fmt
1692
1693 static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE;
1694
1695 /* The kernel command line selection */
1696 enum ssb_mitigation_cmd {
1697 SPEC_STORE_BYPASS_CMD_NONE,
1698 SPEC_STORE_BYPASS_CMD_AUTO,
1699 SPEC_STORE_BYPASS_CMD_ON,
1700 SPEC_STORE_BYPASS_CMD_PRCTL,
1701 SPEC_STORE_BYPASS_CMD_SECCOMP,
1702 };
1703
1704 static const char * const ssb_strings[] = {
1705 [SPEC_STORE_BYPASS_NONE] = "Vulnerable",
1706 [SPEC_STORE_BYPASS_DISABLE] = "Mitigation: Speculative Store Bypass disabled",
1707 [SPEC_STORE_BYPASS_PRCTL] = "Mitigation: Speculative Store Bypass disabled via prctl",
1708 [SPEC_STORE_BYPASS_SECCOMP] = "Mitigation: Speculative Store Bypass disabled via prctl and seccomp",
1709 };
1710
1711 static const struct {
1712 const char *option;
1713 enum ssb_mitigation_cmd cmd;
1714 } ssb_mitigation_options[] __initconst = {
1715 { "auto", SPEC_STORE_BYPASS_CMD_AUTO }, /* Platform decides */
1716 { "on", SPEC_STORE_BYPASS_CMD_ON }, /* Disable Speculative Store Bypass */
1717 { "off", SPEC_STORE_BYPASS_CMD_NONE }, /* Don't touch Speculative Store Bypass */
1718 { "prctl", SPEC_STORE_BYPASS_CMD_PRCTL }, /* Disable Speculative Store Bypass via prctl */
1719 { "seccomp", SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */
1720 };
1721
ssb_parse_cmdline(void)1722 static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
1723 {
1724 enum ssb_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO;
1725 char arg[20];
1726 int ret, i;
1727
1728 if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") ||
1729 cpu_mitigations_off()) {
1730 return SPEC_STORE_BYPASS_CMD_NONE;
1731 } else {
1732 ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
1733 arg, sizeof(arg));
1734 if (ret < 0)
1735 return SPEC_STORE_BYPASS_CMD_AUTO;
1736
1737 for (i = 0; i < ARRAY_SIZE(ssb_mitigation_options); i++) {
1738 if (!match_option(arg, ret, ssb_mitigation_options[i].option))
1739 continue;
1740
1741 cmd = ssb_mitigation_options[i].cmd;
1742 break;
1743 }
1744
1745 if (i >= ARRAY_SIZE(ssb_mitigation_options)) {
1746 pr_err("unknown option (%s). Switching to AUTO select\n", arg);
1747 return SPEC_STORE_BYPASS_CMD_AUTO;
1748 }
1749 }
1750
1751 return cmd;
1752 }
1753
__ssb_select_mitigation(void)1754 static enum ssb_mitigation __init __ssb_select_mitigation(void)
1755 {
1756 enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE;
1757 enum ssb_mitigation_cmd cmd;
1758
1759 if (!boot_cpu_has(X86_FEATURE_SSBD))
1760 return mode;
1761
1762 cmd = ssb_parse_cmdline();
1763 if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) &&
1764 (cmd == SPEC_STORE_BYPASS_CMD_NONE ||
1765 cmd == SPEC_STORE_BYPASS_CMD_AUTO))
1766 return mode;
1767
1768 switch (cmd) {
1769 case SPEC_STORE_BYPASS_CMD_SECCOMP:
1770 /*
1771 * Choose prctl+seccomp as the default mode if seccomp is
1772 * enabled.
1773 */
1774 if (IS_ENABLED(CONFIG_SECCOMP))
1775 mode = SPEC_STORE_BYPASS_SECCOMP;
1776 else
1777 mode = SPEC_STORE_BYPASS_PRCTL;
1778 break;
1779 case SPEC_STORE_BYPASS_CMD_ON:
1780 mode = SPEC_STORE_BYPASS_DISABLE;
1781 break;
1782 case SPEC_STORE_BYPASS_CMD_AUTO:
1783 case SPEC_STORE_BYPASS_CMD_PRCTL:
1784 mode = SPEC_STORE_BYPASS_PRCTL;
1785 break;
1786 case SPEC_STORE_BYPASS_CMD_NONE:
1787 break;
1788 }
1789
1790 /*
1791 * We have three CPU feature flags that are in play here:
1792 * - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible.
1793 * - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass
1794 * - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation
1795 */
1796 if (mode == SPEC_STORE_BYPASS_DISABLE) {
1797 setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE);
1798 /*
1799 * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may
1800 * use a completely different MSR and bit dependent on family.
1801 */
1802 if (!static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) &&
1803 !static_cpu_has(X86_FEATURE_AMD_SSBD)) {
1804 x86_amd_ssb_disable();
1805 } else {
1806 x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
1807 write_spec_ctrl_current(x86_spec_ctrl_base, true);
1808 }
1809 }
1810
1811 return mode;
1812 }
1813
ssb_select_mitigation(void)1814 static void ssb_select_mitigation(void)
1815 {
1816 ssb_mode = __ssb_select_mitigation();
1817
1818 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
1819 pr_info("%s\n", ssb_strings[ssb_mode]);
1820 }
1821
1822 #undef pr_fmt
1823 #define pr_fmt(fmt) "Speculation prctl: " fmt
1824
task_update_spec_tif(struct task_struct * tsk)1825 static void task_update_spec_tif(struct task_struct *tsk)
1826 {
1827 /* Force the update of the real TIF bits */
1828 set_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE);
1829
1830 /*
1831 * Immediately update the speculation control MSRs for the current
1832 * task, but for a non-current task delay setting the CPU
1833 * mitigation until it is scheduled next.
1834 *
1835 * This can only happen for SECCOMP mitigation. For PRCTL it's
1836 * always the current task.
1837 */
1838 if (tsk == current)
1839 speculation_ctrl_update_current();
1840 }
1841
l1d_flush_prctl_set(struct task_struct * task,unsigned long ctrl)1842 static int l1d_flush_prctl_set(struct task_struct *task, unsigned long ctrl)
1843 {
1844
1845 if (!static_branch_unlikely(&switch_mm_cond_l1d_flush))
1846 return -EPERM;
1847
1848 switch (ctrl) {
1849 case PR_SPEC_ENABLE:
1850 set_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH);
1851 return 0;
1852 case PR_SPEC_DISABLE:
1853 clear_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH);
1854 return 0;
1855 default:
1856 return -ERANGE;
1857 }
1858 }
1859
ssb_prctl_set(struct task_struct * task,unsigned long ctrl)1860 static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
1861 {
1862 if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&
1863 ssb_mode != SPEC_STORE_BYPASS_SECCOMP)
1864 return -ENXIO;
1865
1866 switch (ctrl) {
1867 case PR_SPEC_ENABLE:
1868 /* If speculation is force disabled, enable is not allowed */
1869 if (task_spec_ssb_force_disable(task))
1870 return -EPERM;
1871 task_clear_spec_ssb_disable(task);
1872 task_clear_spec_ssb_noexec(task);
1873 task_update_spec_tif(task);
1874 break;
1875 case PR_SPEC_DISABLE:
1876 task_set_spec_ssb_disable(task);
1877 task_clear_spec_ssb_noexec(task);
1878 task_update_spec_tif(task);
1879 break;
1880 case PR_SPEC_FORCE_DISABLE:
1881 task_set_spec_ssb_disable(task);
1882 task_set_spec_ssb_force_disable(task);
1883 task_clear_spec_ssb_noexec(task);
1884 task_update_spec_tif(task);
1885 break;
1886 case PR_SPEC_DISABLE_NOEXEC:
1887 if (task_spec_ssb_force_disable(task))
1888 return -EPERM;
1889 task_set_spec_ssb_disable(task);
1890 task_set_spec_ssb_noexec(task);
1891 task_update_spec_tif(task);
1892 break;
1893 default:
1894 return -ERANGE;
1895 }
1896 return 0;
1897 }
1898
is_spec_ib_user_controlled(void)1899 static bool is_spec_ib_user_controlled(void)
1900 {
1901 return spectre_v2_user_ibpb == SPECTRE_V2_USER_PRCTL ||
1902 spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP ||
1903 spectre_v2_user_stibp == SPECTRE_V2_USER_PRCTL ||
1904 spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP;
1905 }
1906
ib_prctl_set(struct task_struct * task,unsigned long ctrl)1907 static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
1908 {
1909 switch (ctrl) {
1910 case PR_SPEC_ENABLE:
1911 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&
1912 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)
1913 return 0;
1914
1915 /*
1916 * With strict mode for both IBPB and STIBP, the instruction
1917 * code paths avoid checking this task flag and instead,
1918 * unconditionally run the instruction. However, STIBP and IBPB
1919 * are independent and either can be set to conditionally
1920 * enabled regardless of the mode of the other.
1921 *
1922 * If either is set to conditional, allow the task flag to be
1923 * updated, unless it was force-disabled by a previous prctl
1924 * call. Currently, this is possible on an AMD CPU which has the
1925 * feature X86_FEATURE_AMD_STIBP_ALWAYS_ON. In this case, if the
1926 * kernel is booted with 'spectre_v2_user=seccomp', then
1927 * spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP and
1928 * spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED.
1929 */
1930 if (!is_spec_ib_user_controlled() ||
1931 task_spec_ib_force_disable(task))
1932 return -EPERM;
1933
1934 task_clear_spec_ib_disable(task);
1935 task_update_spec_tif(task);
1936 break;
1937 case PR_SPEC_DISABLE:
1938 case PR_SPEC_FORCE_DISABLE:
1939 /*
1940 * Indirect branch speculation is always allowed when
1941 * mitigation is force disabled.
1942 */
1943 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&
1944 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)
1945 return -EPERM;
1946
1947 if (!is_spec_ib_user_controlled())
1948 return 0;
1949
1950 task_set_spec_ib_disable(task);
1951 if (ctrl == PR_SPEC_FORCE_DISABLE)
1952 task_set_spec_ib_force_disable(task);
1953 task_update_spec_tif(task);
1954 break;
1955 default:
1956 return -ERANGE;
1957 }
1958 return 0;
1959 }
1960
arch_prctl_spec_ctrl_set(struct task_struct * task,unsigned long which,unsigned long ctrl)1961 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
1962 unsigned long ctrl)
1963 {
1964 switch (which) {
1965 case PR_SPEC_STORE_BYPASS:
1966 return ssb_prctl_set(task, ctrl);
1967 case PR_SPEC_INDIRECT_BRANCH:
1968 return ib_prctl_set(task, ctrl);
1969 case PR_SPEC_L1D_FLUSH:
1970 return l1d_flush_prctl_set(task, ctrl);
1971 default:
1972 return -ENODEV;
1973 }
1974 }
1975
1976 #ifdef CONFIG_SECCOMP
arch_seccomp_spec_mitigate(struct task_struct * task)1977 void arch_seccomp_spec_mitigate(struct task_struct *task)
1978 {
1979 if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
1980 ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
1981 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_SECCOMP ||
1982 spectre_v2_user_stibp == SPECTRE_V2_USER_SECCOMP)
1983 ib_prctl_set(task, PR_SPEC_FORCE_DISABLE);
1984 }
1985 #endif
1986
l1d_flush_prctl_get(struct task_struct * task)1987 static int l1d_flush_prctl_get(struct task_struct *task)
1988 {
1989 if (!static_branch_unlikely(&switch_mm_cond_l1d_flush))
1990 return PR_SPEC_FORCE_DISABLE;
1991
1992 if (test_ti_thread_flag(&task->thread_info, TIF_SPEC_L1D_FLUSH))
1993 return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
1994 else
1995 return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
1996 }
1997
ssb_prctl_get(struct task_struct * task)1998 static int ssb_prctl_get(struct task_struct *task)
1999 {
2000 switch (ssb_mode) {
2001 case SPEC_STORE_BYPASS_DISABLE:
2002 return PR_SPEC_DISABLE;
2003 case SPEC_STORE_BYPASS_SECCOMP:
2004 case SPEC_STORE_BYPASS_PRCTL:
2005 if (task_spec_ssb_force_disable(task))
2006 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
2007 if (task_spec_ssb_noexec(task))
2008 return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC;
2009 if (task_spec_ssb_disable(task))
2010 return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
2011 return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
2012 default:
2013 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
2014 return PR_SPEC_ENABLE;
2015 return PR_SPEC_NOT_AFFECTED;
2016 }
2017 }
2018
ib_prctl_get(struct task_struct * task)2019 static int ib_prctl_get(struct task_struct *task)
2020 {
2021 if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
2022 return PR_SPEC_NOT_AFFECTED;
2023
2024 if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&
2025 spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)
2026 return PR_SPEC_ENABLE;
2027 else if (is_spec_ib_user_controlled()) {
2028 if (task_spec_ib_force_disable(task))
2029 return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
2030 if (task_spec_ib_disable(task))
2031 return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
2032 return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
2033 } else if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT ||
2034 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||
2035 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED)
2036 return PR_SPEC_DISABLE;
2037 else
2038 return PR_SPEC_NOT_AFFECTED;
2039 }
2040
arch_prctl_spec_ctrl_get(struct task_struct * task,unsigned long which)2041 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
2042 {
2043 switch (which) {
2044 case PR_SPEC_STORE_BYPASS:
2045 return ssb_prctl_get(task);
2046 case PR_SPEC_INDIRECT_BRANCH:
2047 return ib_prctl_get(task);
2048 case PR_SPEC_L1D_FLUSH:
2049 return l1d_flush_prctl_get(task);
2050 default:
2051 return -ENODEV;
2052 }
2053 }
2054
x86_spec_ctrl_setup_ap(void)2055 void x86_spec_ctrl_setup_ap(void)
2056 {
2057 if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
2058 write_spec_ctrl_current(x86_spec_ctrl_base, true);
2059
2060 if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
2061 x86_amd_ssb_disable();
2062 }
2063
2064 bool itlb_multihit_kvm_mitigation;
2065 EXPORT_SYMBOL_GPL(itlb_multihit_kvm_mitigation);
2066
2067 #undef pr_fmt
2068 #define pr_fmt(fmt) "L1TF: " fmt
2069
2070 /* Default mitigation for L1TF-affected CPUs */
2071 enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH;
2072 #if IS_ENABLED(CONFIG_KVM_INTEL)
2073 EXPORT_SYMBOL_GPL(l1tf_mitigation);
2074 #endif
2075 enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
2076 EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation);
2077
2078 /*
2079 * These CPUs all support 44bits physical address space internally in the
2080 * cache but CPUID can report a smaller number of physical address bits.
2081 *
2082 * The L1TF mitigation uses the top most address bit for the inversion of
2083 * non present PTEs. When the installed memory reaches into the top most
2084 * address bit due to memory holes, which has been observed on machines
2085 * which report 36bits physical address bits and have 32G RAM installed,
2086 * then the mitigation range check in l1tf_select_mitigation() triggers.
2087 * This is a false positive because the mitigation is still possible due to
2088 * the fact that the cache uses 44bit internally. Use the cache bits
2089 * instead of the reported physical bits and adjust them on the affected
2090 * machines to 44bit if the reported bits are less than 44.
2091 */
override_cache_bits(struct cpuinfo_x86 * c)2092 static void override_cache_bits(struct cpuinfo_x86 *c)
2093 {
2094 if (c->x86 != 6)
2095 return;
2096
2097 switch (c->x86_model) {
2098 case INTEL_FAM6_NEHALEM:
2099 case INTEL_FAM6_WESTMERE:
2100 case INTEL_FAM6_SANDYBRIDGE:
2101 case INTEL_FAM6_IVYBRIDGE:
2102 case INTEL_FAM6_HASWELL:
2103 case INTEL_FAM6_HASWELL_L:
2104 case INTEL_FAM6_HASWELL_G:
2105 case INTEL_FAM6_BROADWELL:
2106 case INTEL_FAM6_BROADWELL_G:
2107 case INTEL_FAM6_SKYLAKE_L:
2108 case INTEL_FAM6_SKYLAKE:
2109 case INTEL_FAM6_KABYLAKE_L:
2110 case INTEL_FAM6_KABYLAKE:
2111 if (c->x86_cache_bits < 44)
2112 c->x86_cache_bits = 44;
2113 break;
2114 }
2115 }
2116
l1tf_select_mitigation(void)2117 static void __init l1tf_select_mitigation(void)
2118 {
2119 u64 half_pa;
2120
2121 if (!boot_cpu_has_bug(X86_BUG_L1TF))
2122 return;
2123
2124 if (cpu_mitigations_off())
2125 l1tf_mitigation = L1TF_MITIGATION_OFF;
2126 else if (cpu_mitigations_auto_nosmt())
2127 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
2128
2129 override_cache_bits(&boot_cpu_data);
2130
2131 switch (l1tf_mitigation) {
2132 case L1TF_MITIGATION_OFF:
2133 case L1TF_MITIGATION_FLUSH_NOWARN:
2134 case L1TF_MITIGATION_FLUSH:
2135 break;
2136 case L1TF_MITIGATION_FLUSH_NOSMT:
2137 case L1TF_MITIGATION_FULL:
2138 cpu_smt_disable(false);
2139 break;
2140 case L1TF_MITIGATION_FULL_FORCE:
2141 cpu_smt_disable(true);
2142 break;
2143 }
2144
2145 #if CONFIG_PGTABLE_LEVELS == 2
2146 pr_warn("Kernel not compiled for PAE. No mitigation for L1TF\n");
2147 return;
2148 #endif
2149
2150 half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT;
2151 if (l1tf_mitigation != L1TF_MITIGATION_OFF &&
2152 e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) {
2153 pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n");
2154 pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n",
2155 half_pa);
2156 pr_info("However, doing so will make a part of your RAM unusable.\n");
2157 pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html might help you decide.\n");
2158 return;
2159 }
2160
2161 setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV);
2162 }
2163
l1tf_cmdline(char * str)2164 static int __init l1tf_cmdline(char *str)
2165 {
2166 if (!boot_cpu_has_bug(X86_BUG_L1TF))
2167 return 0;
2168
2169 if (!str)
2170 return -EINVAL;
2171
2172 if (!strcmp(str, "off"))
2173 l1tf_mitigation = L1TF_MITIGATION_OFF;
2174 else if (!strcmp(str, "flush,nowarn"))
2175 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOWARN;
2176 else if (!strcmp(str, "flush"))
2177 l1tf_mitigation = L1TF_MITIGATION_FLUSH;
2178 else if (!strcmp(str, "flush,nosmt"))
2179 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
2180 else if (!strcmp(str, "full"))
2181 l1tf_mitigation = L1TF_MITIGATION_FULL;
2182 else if (!strcmp(str, "full,force"))
2183 l1tf_mitigation = L1TF_MITIGATION_FULL_FORCE;
2184
2185 return 0;
2186 }
2187 early_param("l1tf", l1tf_cmdline);
2188
2189 #undef pr_fmt
2190 #define pr_fmt(fmt) fmt
2191
2192 #ifdef CONFIG_SYSFS
2193
2194 #define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion"
2195
2196 #if IS_ENABLED(CONFIG_KVM_INTEL)
2197 static const char * const l1tf_vmx_states[] = {
2198 [VMENTER_L1D_FLUSH_AUTO] = "auto",
2199 [VMENTER_L1D_FLUSH_NEVER] = "vulnerable",
2200 [VMENTER_L1D_FLUSH_COND] = "conditional cache flushes",
2201 [VMENTER_L1D_FLUSH_ALWAYS] = "cache flushes",
2202 [VMENTER_L1D_FLUSH_EPT_DISABLED] = "EPT disabled",
2203 [VMENTER_L1D_FLUSH_NOT_REQUIRED] = "flush not necessary"
2204 };
2205
l1tf_show_state(char * buf)2206 static ssize_t l1tf_show_state(char *buf)
2207 {
2208 if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_AUTO)
2209 return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG);
2210
2211 if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_EPT_DISABLED ||
2212 (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER &&
2213 sched_smt_active())) {
2214 return sprintf(buf, "%s; VMX: %s\n", L1TF_DEFAULT_MSG,
2215 l1tf_vmx_states[l1tf_vmx_mitigation]);
2216 }
2217
2218 return sprintf(buf, "%s; VMX: %s, SMT %s\n", L1TF_DEFAULT_MSG,
2219 l1tf_vmx_states[l1tf_vmx_mitigation],
2220 sched_smt_active() ? "vulnerable" : "disabled");
2221 }
2222
itlb_multihit_show_state(char * buf)2223 static ssize_t itlb_multihit_show_state(char *buf)
2224 {
2225 if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) ||
2226 !boot_cpu_has(X86_FEATURE_VMX))
2227 return sprintf(buf, "KVM: Mitigation: VMX unsupported\n");
2228 else if (!(cr4_read_shadow() & X86_CR4_VMXE))
2229 return sprintf(buf, "KVM: Mitigation: VMX disabled\n");
2230 else if (itlb_multihit_kvm_mitigation)
2231 return sprintf(buf, "KVM: Mitigation: Split huge pages\n");
2232 else
2233 return sprintf(buf, "KVM: Vulnerable\n");
2234 }
2235 #else
l1tf_show_state(char * buf)2236 static ssize_t l1tf_show_state(char *buf)
2237 {
2238 return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG);
2239 }
2240
itlb_multihit_show_state(char * buf)2241 static ssize_t itlb_multihit_show_state(char *buf)
2242 {
2243 return sprintf(buf, "Processor vulnerable\n");
2244 }
2245 #endif
2246
mds_show_state(char * buf)2247 static ssize_t mds_show_state(char *buf)
2248 {
2249 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
2250 return sprintf(buf, "%s; SMT Host state unknown\n",
2251 mds_strings[mds_mitigation]);
2252 }
2253
2254 if (boot_cpu_has(X86_BUG_MSBDS_ONLY)) {
2255 return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],
2256 (mds_mitigation == MDS_MITIGATION_OFF ? "vulnerable" :
2257 sched_smt_active() ? "mitigated" : "disabled"));
2258 }
2259
2260 return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],
2261 sched_smt_active() ? "vulnerable" : "disabled");
2262 }
2263
tsx_async_abort_show_state(char * buf)2264 static ssize_t tsx_async_abort_show_state(char *buf)
2265 {
2266 if ((taa_mitigation == TAA_MITIGATION_TSX_DISABLED) ||
2267 (taa_mitigation == TAA_MITIGATION_OFF))
2268 return sprintf(buf, "%s\n", taa_strings[taa_mitigation]);
2269
2270 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
2271 return sprintf(buf, "%s; SMT Host state unknown\n",
2272 taa_strings[taa_mitigation]);
2273 }
2274
2275 return sprintf(buf, "%s; SMT %s\n", taa_strings[taa_mitigation],
2276 sched_smt_active() ? "vulnerable" : "disabled");
2277 }
2278
mmio_stale_data_show_state(char * buf)2279 static ssize_t mmio_stale_data_show_state(char *buf)
2280 {
2281 if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
2282 return sysfs_emit(buf, "Unknown: No mitigations\n");
2283
2284 if (mmio_mitigation == MMIO_MITIGATION_OFF)
2285 return sysfs_emit(buf, "%s\n", mmio_strings[mmio_mitigation]);
2286
2287 if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
2288 return sysfs_emit(buf, "%s; SMT Host state unknown\n",
2289 mmio_strings[mmio_mitigation]);
2290 }
2291
2292 return sysfs_emit(buf, "%s; SMT %s\n", mmio_strings[mmio_mitigation],
2293 sched_smt_active() ? "vulnerable" : "disabled");
2294 }
2295
stibp_state(void)2296 static char *stibp_state(void)
2297 {
2298 if (spectre_v2_in_ibrs_mode(spectre_v2_enabled))
2299 return "";
2300
2301 switch (spectre_v2_user_stibp) {
2302 case SPECTRE_V2_USER_NONE:
2303 return ", STIBP: disabled";
2304 case SPECTRE_V2_USER_STRICT:
2305 return ", STIBP: forced";
2306 case SPECTRE_V2_USER_STRICT_PREFERRED:
2307 return ", STIBP: always-on";
2308 case SPECTRE_V2_USER_PRCTL:
2309 case SPECTRE_V2_USER_SECCOMP:
2310 if (static_key_enabled(&switch_to_cond_stibp))
2311 return ", STIBP: conditional";
2312 }
2313 return "";
2314 }
2315
ibpb_state(void)2316 static char *ibpb_state(void)
2317 {
2318 if (boot_cpu_has(X86_FEATURE_IBPB)) {
2319 if (static_key_enabled(&switch_mm_always_ibpb))
2320 return ", IBPB: always-on";
2321 if (static_key_enabled(&switch_mm_cond_ibpb))
2322 return ", IBPB: conditional";
2323 return ", IBPB: disabled";
2324 }
2325 return "";
2326 }
2327
pbrsb_eibrs_state(void)2328 static char *pbrsb_eibrs_state(void)
2329 {
2330 if (boot_cpu_has_bug(X86_BUG_EIBRS_PBRSB)) {
2331 if (boot_cpu_has(X86_FEATURE_RSB_VMEXIT_LITE) ||
2332 boot_cpu_has(X86_FEATURE_RSB_VMEXIT))
2333 return ", PBRSB-eIBRS: SW sequence";
2334 else
2335 return ", PBRSB-eIBRS: Vulnerable";
2336 } else {
2337 return ", PBRSB-eIBRS: Not affected";
2338 }
2339 }
2340
spectre_v2_show_state(char * buf)2341 static ssize_t spectre_v2_show_state(char *buf)
2342 {
2343 if (spectre_v2_enabled == SPECTRE_V2_LFENCE)
2344 return sprintf(buf, "Vulnerable: LFENCE\n");
2345
2346 if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())
2347 return sprintf(buf, "Vulnerable: eIBRS with unprivileged eBPF\n");
2348
2349 if (sched_smt_active() && unprivileged_ebpf_enabled() &&
2350 spectre_v2_enabled == SPECTRE_V2_EIBRS_LFENCE)
2351 return sprintf(buf, "Vulnerable: eIBRS+LFENCE with unprivileged eBPF and SMT\n");
2352
2353 return sprintf(buf, "%s%s%s%s%s%s%s\n",
2354 spectre_v2_strings[spectre_v2_enabled],
2355 ibpb_state(),
2356 boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
2357 stibp_state(),
2358 boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
2359 pbrsb_eibrs_state(),
2360 spectre_v2_module_string());
2361 }
2362
srbds_show_state(char * buf)2363 static ssize_t srbds_show_state(char *buf)
2364 {
2365 return sprintf(buf, "%s\n", srbds_strings[srbds_mitigation]);
2366 }
2367
retbleed_show_state(char * buf)2368 static ssize_t retbleed_show_state(char *buf)
2369 {
2370 if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET ||
2371 retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
2372 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
2373 boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
2374 return sprintf(buf, "Vulnerable: untrained return thunk / IBPB on non-AMD based uarch\n");
2375
2376 return sprintf(buf, "%s; SMT %s\n",
2377 retbleed_strings[retbleed_mitigation],
2378 !sched_smt_active() ? "disabled" :
2379 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||
2380 spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED ?
2381 "enabled with STIBP protection" : "vulnerable");
2382 }
2383
2384 return sprintf(buf, "%s\n", retbleed_strings[retbleed_mitigation]);
2385 }
2386
cpu_show_common(struct device * dev,struct device_attribute * attr,char * buf,unsigned int bug)2387 static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
2388 char *buf, unsigned int bug)
2389 {
2390 if (!boot_cpu_has_bug(bug))
2391 return sprintf(buf, "Not affected\n");
2392
2393 switch (bug) {
2394 case X86_BUG_CPU_MELTDOWN:
2395 if (boot_cpu_has(X86_FEATURE_PTI))
2396 return sprintf(buf, "Mitigation: PTI\n");
2397
2398 if (hypervisor_is_type(X86_HYPER_XEN_PV))
2399 return sprintf(buf, "Unknown (XEN PV detected, hypervisor mitigation required)\n");
2400
2401 break;
2402
2403 case X86_BUG_SPECTRE_V1:
2404 return sprintf(buf, "%s\n", spectre_v1_strings[spectre_v1_mitigation]);
2405
2406 case X86_BUG_SPECTRE_V2:
2407 return spectre_v2_show_state(buf);
2408
2409 case X86_BUG_SPEC_STORE_BYPASS:
2410 return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);
2411
2412 case X86_BUG_L1TF:
2413 if (boot_cpu_has(X86_FEATURE_L1TF_PTEINV))
2414 return l1tf_show_state(buf);
2415 break;
2416
2417 case X86_BUG_MDS:
2418 return mds_show_state(buf);
2419
2420 case X86_BUG_TAA:
2421 return tsx_async_abort_show_state(buf);
2422
2423 case X86_BUG_ITLB_MULTIHIT:
2424 return itlb_multihit_show_state(buf);
2425
2426 case X86_BUG_SRBDS:
2427 return srbds_show_state(buf);
2428
2429 case X86_BUG_MMIO_STALE_DATA:
2430 case X86_BUG_MMIO_UNKNOWN:
2431 return mmio_stale_data_show_state(buf);
2432
2433 case X86_BUG_RETBLEED:
2434 return retbleed_show_state(buf);
2435
2436 default:
2437 break;
2438 }
2439
2440 return sprintf(buf, "Vulnerable\n");
2441 }
2442
cpu_show_meltdown(struct device * dev,struct device_attribute * attr,char * buf)2443 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
2444 {
2445 return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN);
2446 }
2447
cpu_show_spectre_v1(struct device * dev,struct device_attribute * attr,char * buf)2448 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
2449 {
2450 return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1);
2451 }
2452
cpu_show_spectre_v2(struct device * dev,struct device_attribute * attr,char * buf)2453 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
2454 {
2455 return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2);
2456 }
2457
cpu_show_spec_store_bypass(struct device * dev,struct device_attribute * attr,char * buf)2458 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
2459 {
2460 return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS);
2461 }
2462
cpu_show_l1tf(struct device * dev,struct device_attribute * attr,char * buf)2463 ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
2464 {
2465 return cpu_show_common(dev, attr, buf, X86_BUG_L1TF);
2466 }
2467
cpu_show_mds(struct device * dev,struct device_attribute * attr,char * buf)2468 ssize_t cpu_show_mds(struct device *dev, struct device_attribute *attr, char *buf)
2469 {
2470 return cpu_show_common(dev, attr, buf, X86_BUG_MDS);
2471 }
2472
cpu_show_tsx_async_abort(struct device * dev,struct device_attribute * attr,char * buf)2473 ssize_t cpu_show_tsx_async_abort(struct device *dev, struct device_attribute *attr, char *buf)
2474 {
2475 return cpu_show_common(dev, attr, buf, X86_BUG_TAA);
2476 }
2477
cpu_show_itlb_multihit(struct device * dev,struct device_attribute * attr,char * buf)2478 ssize_t cpu_show_itlb_multihit(struct device *dev, struct device_attribute *attr, char *buf)
2479 {
2480 return cpu_show_common(dev, attr, buf, X86_BUG_ITLB_MULTIHIT);
2481 }
2482
cpu_show_srbds(struct device * dev,struct device_attribute * attr,char * buf)2483 ssize_t cpu_show_srbds(struct device *dev, struct device_attribute *attr, char *buf)
2484 {
2485 return cpu_show_common(dev, attr, buf, X86_BUG_SRBDS);
2486 }
2487
cpu_show_mmio_stale_data(struct device * dev,struct device_attribute * attr,char * buf)2488 ssize_t cpu_show_mmio_stale_data(struct device *dev, struct device_attribute *attr, char *buf)
2489 {
2490 if (boot_cpu_has_bug(X86_BUG_MMIO_UNKNOWN))
2491 return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_UNKNOWN);
2492 else
2493 return cpu_show_common(dev, attr, buf, X86_BUG_MMIO_STALE_DATA);
2494 }
2495
cpu_show_retbleed(struct device * dev,struct device_attribute * attr,char * buf)2496 ssize_t cpu_show_retbleed(struct device *dev, struct device_attribute *attr, char *buf)
2497 {
2498 return cpu_show_common(dev, attr, buf, X86_BUG_RETBLEED);
2499 }
2500 #endif
2501