1 /*
2  * Copyright (c) 2019 Alexey Dobriyan <adobriyan@gmail.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 /*
17  * Fork and exec tiny 1 page executable which precisely controls its VM.
18  * Test /proc/$PID/maps
19  * Test /proc/$PID/smaps
20  * Test /proc/$PID/smaps_rollup
21  * Test /proc/$PID/statm
22  *
23  * FIXME require CONFIG_TMPFS which can be disabled
24  * FIXME test other values from "smaps"
25  * FIXME support other archs
26  */
27 #undef NDEBUG
28 #include <assert.h>
29 #include <errno.h>
30 #include <sched.h>
31 #include <signal.h>
32 #include <stdbool.h>
33 #include <stdint.h>
34 #include <stdio.h>
35 #include <string.h>
36 #include <stdlib.h>
37 #include <sys/mount.h>
38 #include <sys/types.h>
39 #include <sys/stat.h>
40 #include <sys/wait.h>
41 #include <fcntl.h>
42 #include <unistd.h>
43 #include <sys/syscall.h>
44 #include <sys/uio.h>
45 #include <linux/kdev_t.h>
46 #include <sys/time.h>
47 #include <sys/resource.h>
48 
49 #include "../kselftest.h"
50 
sys_execveat(int dirfd,const char * pathname,char ** argv,char ** envp,int flags)51 static inline long sys_execveat(int dirfd, const char *pathname, char **argv, char **envp, int flags)
52 {
53 	return syscall(SYS_execveat, dirfd, pathname, argv, envp, flags);
54 }
55 
make_private_tmp(void)56 static void make_private_tmp(void)
57 {
58 	if (unshare(CLONE_NEWNS) == -1) {
59 		if (errno == ENOSYS || errno == EPERM) {
60 			exit(4);
61 		}
62 		exit(1);
63 	}
64 	if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) == -1) {
65 		exit(1);
66 	}
67 	if (mount(NULL, "/tmp", "tmpfs", 0, NULL) == -1) {
68 		exit(1);
69 	}
70 }
71 
72 static pid_t pid = -1;
ate(void)73 static void ate(void)
74 {
75 	if (pid > 0) {
76 		kill(pid, SIGTERM);
77 	}
78 }
79 
80 struct elf64_hdr {
81 	uint8_t e_ident[16];
82 	uint16_t e_type;
83 	uint16_t e_machine;
84 	uint32_t e_version;
85 	uint64_t e_entry;
86 	uint64_t e_phoff;
87 	uint64_t e_shoff;
88 	uint32_t e_flags;
89 	uint16_t e_ehsize;
90 	uint16_t e_phentsize;
91 	uint16_t e_phnum;
92 	uint16_t e_shentsize;
93 	uint16_t e_shnum;
94 	uint16_t e_shstrndx;
95 };
96 
97 struct elf64_phdr {
98 	uint32_t p_type;
99 	uint32_t p_flags;
100 	uint64_t p_offset;
101 	uint64_t p_vaddr;
102 	uint64_t p_paddr;
103 	uint64_t p_filesz;
104 	uint64_t p_memsz;
105 	uint64_t p_align;
106 };
107 
108 #ifdef __x86_64__
109 #define PAGE_SIZE 4096
110 #define VADDR (1UL << 32)
111 #define MAPS_OFFSET 73
112 
113 #define syscall	0x0f, 0x05
114 #define mov_rdi(x)	\
115 	0x48, 0xbf,	\
116 	(x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff,	\
117 	((x)>>32)&0xff, ((x)>>40)&0xff, ((x)>>48)&0xff, ((x)>>56)&0xff
118 
119 #define mov_rsi(x)	\
120 	0x48, 0xbe,	\
121 	(x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff,	\
122 	((x)>>32)&0xff, ((x)>>40)&0xff, ((x)>>48)&0xff, ((x)>>56)&0xff
123 
124 #define mov_eax(x)	\
125 	0xb8, (x)&0xff, ((x)>>8)&0xff, ((x)>>16)&0xff, ((x)>>24)&0xff
126 
127 static const uint8_t payload[] = {
128 	/* Casually unmap stack, vDSO and everything else. */
129 	/* munmap */
130 	mov_rdi(VADDR + 4096),
131 	mov_rsi((1ULL << 47) - 4096 - VADDR - 4096),
132 	mov_eax(11),
133 	syscall,
134 
135 	/* Ping parent. */
136 	/* write(0, &c, 1); */
137 	0x31, 0xff,					/* xor edi, edi */
138 	0x48, 0x8d, 0x35, 0x00, 0x00, 0x00, 0x00,	/* lea rsi, [rip] */
139 	0xba, 0x01, 0x00, 0x00, 0x00,			/* mov edx, 1 */
140 	mov_eax(1),
141 	syscall,
142 
143 	/* 1: pause(); */
144 	mov_eax(34),
145 	syscall,
146 
147 	0xeb, 0xf7,	/* jmp 1b */
148 };
149 
make_exe(const uint8_t * payload,size_t len)150 static int make_exe(const uint8_t *payload, size_t len)
151 {
152 	struct elf64_hdr h;
153 	struct elf64_phdr ph;
154 
155 	struct iovec iov[3] = {
156 		{&h, sizeof(struct elf64_hdr)},
157 		{&ph, sizeof(struct elf64_phdr)},
158 		{(void *)payload, len},
159 	};
160 	int fd, fd1;
161 	char buf[64];
162 
163 	memset(&h, 0, sizeof(h));
164 	h.e_ident[0] = 0x7f;
165 	h.e_ident[1] = 'E';
166 	h.e_ident[2] = 'L';
167 	h.e_ident[3] = 'F';
168 	h.e_ident[4] = 2;
169 	h.e_ident[5] = 1;
170 	h.e_ident[6] = 1;
171 	h.e_ident[7] = 0;
172 	h.e_type = 2;
173 	h.e_machine = 0x3e;
174 	h.e_version = 1;
175 	h.e_entry = VADDR + sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr);
176 	h.e_phoff = sizeof(struct elf64_hdr);
177 	h.e_shoff = 0;
178 	h.e_flags = 0;
179 	h.e_ehsize = sizeof(struct elf64_hdr);
180 	h.e_phentsize = sizeof(struct elf64_phdr);
181 	h.e_phnum = 1;
182 	h.e_shentsize = 0;
183 	h.e_shnum = 0;
184 	h.e_shstrndx = 0;
185 
186 	memset(&ph, 0, sizeof(ph));
187 	ph.p_type = 1;
188 	ph.p_flags = (1<<2)|1;
189 	ph.p_offset = 0;
190 	ph.p_vaddr = VADDR;
191 	ph.p_paddr = 0;
192 	ph.p_filesz = sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len;
193 	ph.p_memsz = sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len;
194 	ph.p_align = 4096;
195 
196 	fd = openat(AT_FDCWD, "/tmp", O_WRONLY|O_EXCL|O_TMPFILE, 0700);
197 	if (fd == -1) {
198 		exit(1);
199 	}
200 
201 	if (writev(fd, iov, 3) != sizeof(struct elf64_hdr) + sizeof(struct elf64_phdr) + len) {
202 		exit(1);
203 	}
204 
205 	/* Avoid ETXTBSY on exec. */
206 	snprintf(buf, sizeof(buf), "/proc/self/fd/%u", fd);
207 	fd1 = open(buf, O_RDONLY|O_CLOEXEC);
208 	close(fd);
209 
210 	return fd1;
211 }
212 #endif
213 
214 static bool g_vsyscall = false;
215 
216 static const char str_vsyscall[] =
217 "ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]\n";
218 
219 #ifdef __x86_64__
sigaction_SIGSEGV(int _,siginfo_t * __,void * ___)220 static void sigaction_SIGSEGV(int _, siginfo_t *__, void *___)
221 {
222 	_exit(1);
223 }
224 
225 /*
226  * vsyscall page can't be unmapped, probe it with memory load.
227  */
vsyscall(void)228 static void vsyscall(void)
229 {
230 	pid_t pid;
231 	int wstatus;
232 
233 	pid = fork();
234 	if (pid < 0) {
235 		fprintf(stderr, "fork, errno %d\n", errno);
236 		exit(1);
237 	}
238 	if (pid == 0) {
239 		struct rlimit rlim = {0, 0};
240 		(void)setrlimit(RLIMIT_CORE, &rlim);
241 
242 		/* Hide "segfault at ffffffffff600000" messages. */
243 		struct sigaction act;
244 		memset(&act, 0, sizeof(struct sigaction));
245 		act.sa_flags = SA_SIGINFO;
246 		act.sa_sigaction = sigaction_SIGSEGV;
247 		(void)sigaction(SIGSEGV, &act, NULL);
248 
249 		*(volatile int *)0xffffffffff600000UL;
250 		exit(0);
251 	}
252 	waitpid(pid, &wstatus, 0);
253 	if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0) {
254 		g_vsyscall = true;
255 	}
256 }
257 
main(void)258 int main(void)
259 {
260 	int pipefd[2];
261 	int exec_fd;
262 
263 	vsyscall();
264 
265 	atexit(ate);
266 
267 	make_private_tmp();
268 
269 	/* Reserve fd 0 for 1-byte pipe ping from child. */
270 	close(0);
271 	if (open("/", O_RDONLY|O_DIRECTORY|O_PATH) != 0) {
272 		return 1;
273 	}
274 
275 	exec_fd = make_exe(payload, sizeof(payload));
276 
277 	if (pipe(pipefd) == -1) {
278 		return 1;
279 	}
280 	if (dup2(pipefd[1], 0) != 0) {
281 		return 1;
282 	}
283 
284 	pid = fork();
285 	if (pid == -1) {
286 		return 1;
287 	}
288 	if (pid == 0) {
289 		sys_execveat(exec_fd, "", NULL, NULL, AT_EMPTY_PATH);
290 		return 1;
291 	}
292 
293 	char _;
294 	if (read(pipefd[0], &_, 1) != 1) {
295 		return 1;
296 	}
297 
298 	struct stat st;
299 	if (fstat(exec_fd, &st) == -1) {
300 		return 1;
301 	}
302 
303 	/* Generate "head -n1 /proc/$PID/maps" */
304 	char buf0[256];
305 	memset(buf0, ' ', sizeof(buf0));
306 	int len = snprintf(buf0, sizeof(buf0),
307 			"%08lx-%08lx r-xp 00000000 %02lx:%02lx %llu",
308 			VADDR, VADDR + PAGE_SIZE,
309 			MAJOR(st.st_dev), MINOR(st.st_dev),
310 			(unsigned long long)st.st_ino);
311 	buf0[len] = ' ';
312 	snprintf(buf0 + MAPS_OFFSET, sizeof(buf0) - MAPS_OFFSET,
313 		 "/tmp/#%llu (deleted)\n", (unsigned long long)st.st_ino);
314 
315 	/* Test /proc/$PID/maps */
316 	{
317 		const size_t len = strlen(buf0) + (g_vsyscall ? strlen(str_vsyscall) : 0);
318 		char buf[256];
319 		ssize_t rv;
320 		int fd;
321 
322 		snprintf(buf, sizeof(buf), "/proc/%u/maps", pid);
323 		fd = open(buf, O_RDONLY);
324 		if (fd == -1) {
325 			return 1;
326 		}
327 		rv = read(fd, buf, sizeof(buf));
328 		assert(rv == len);
329 		assert(memcmp(buf, buf0, strlen(buf0)) == 0);
330 		if (g_vsyscall) {
331 			assert(memcmp(buf + strlen(buf0), str_vsyscall, strlen(str_vsyscall)) == 0);
332 		}
333 	}
334 
335 	/* Test /proc/$PID/smaps */
336 	{
337 		char buf[4096];
338 		ssize_t rv;
339 		int fd;
340 
341 		snprintf(buf, sizeof(buf), "/proc/%u/smaps", pid);
342 		fd = open(buf, O_RDONLY);
343 		if (fd == -1) {
344 			return 1;
345 		}
346 		rv = read(fd, buf, sizeof(buf));
347 		assert(0 <= rv && rv <= sizeof(buf));
348 
349 		assert(rv >= strlen(buf0));
350 		assert(memcmp(buf, buf0, strlen(buf0)) == 0);
351 
352 #define RSS1 "Rss:                   4 kB\n"
353 #define RSS2 "Rss:                   0 kB\n"
354 #define PSS1 "Pss:                   4 kB\n"
355 #define PSS2 "Pss:                   0 kB\n"
356 		assert(memmem(buf, rv, RSS1, strlen(RSS1)) ||
357 		       memmem(buf, rv, RSS2, strlen(RSS2)));
358 		assert(memmem(buf, rv, PSS1, strlen(PSS1)) ||
359 		       memmem(buf, rv, PSS2, strlen(PSS2)));
360 
361 		static const char *S[] = {
362 			"Size:                  4 kB\n",
363 			"KernelPageSize:        4 kB\n",
364 			"MMUPageSize:           4 kB\n",
365 			"Anonymous:             0 kB\n",
366 			"AnonHugePages:         0 kB\n",
367 			"Shared_Hugetlb:        0 kB\n",
368 			"Private_Hugetlb:       0 kB\n",
369 			"Locked:                0 kB\n",
370 		};
371 		int i;
372 
373 		for (i = 0; i < ARRAY_SIZE(S); i++) {
374 			assert(memmem(buf, rv, S[i], strlen(S[i])));
375 		}
376 
377 		if (g_vsyscall) {
378 			assert(memmem(buf, rv, str_vsyscall, strlen(str_vsyscall)));
379 		}
380 	}
381 
382 	/* Test /proc/$PID/smaps_rollup */
383 	{
384 		char bufr[256];
385 		memset(bufr, ' ', sizeof(bufr));
386 		len = snprintf(bufr, sizeof(bufr),
387 				"%08lx-%08lx ---p 00000000 00:00 0",
388 				VADDR, VADDR + PAGE_SIZE);
389 		bufr[len] = ' ';
390 		snprintf(bufr + MAPS_OFFSET, sizeof(bufr) - MAPS_OFFSET,
391 			 "[rollup]\n");
392 
393 		char buf[1024];
394 		ssize_t rv;
395 		int fd;
396 
397 		snprintf(buf, sizeof(buf), "/proc/%u/smaps_rollup", pid);
398 		fd = open(buf, O_RDONLY);
399 		if (fd == -1) {
400 			return 1;
401 		}
402 		rv = read(fd, buf, sizeof(buf));
403 		assert(0 <= rv && rv <= sizeof(buf));
404 
405 		assert(rv >= strlen(bufr));
406 		assert(memcmp(buf, bufr, strlen(bufr)) == 0);
407 
408 		assert(memmem(buf, rv, RSS1, strlen(RSS1)) ||
409 		       memmem(buf, rv, RSS2, strlen(RSS2)));
410 		assert(memmem(buf, rv, PSS1, strlen(PSS1)) ||
411 		       memmem(buf, rv, PSS2, strlen(PSS2)));
412 
413 		static const char *S[] = {
414 			"Anonymous:             0 kB\n",
415 			"AnonHugePages:         0 kB\n",
416 			"Shared_Hugetlb:        0 kB\n",
417 			"Private_Hugetlb:       0 kB\n",
418 			"Locked:                0 kB\n",
419 		};
420 		int i;
421 
422 		for (i = 0; i < ARRAY_SIZE(S); i++) {
423 			assert(memmem(buf, rv, S[i], strlen(S[i])));
424 		}
425 	}
426 
427 	/* Test /proc/$PID/statm */
428 	{
429 		char buf[64];
430 		ssize_t rv;
431 		int fd;
432 
433 		snprintf(buf, sizeof(buf), "/proc/%u/statm", pid);
434 		fd = open(buf, O_RDONLY);
435 		if (fd == -1) {
436 			return 1;
437 		}
438 		rv = read(fd, buf, sizeof(buf));
439 		assert(rv == 7 * 2);
440 
441 		assert(buf[0] == '1');	/* ->total_vm */
442 		assert(buf[1] == ' ');
443 		assert(buf[2] == '0' || buf[2] == '1');	/* rss */
444 		assert(buf[3] == ' ');
445 		assert(buf[4] == '0' || buf[2] == '1');	/* file rss */
446 		assert(buf[5] == ' ');
447 		assert(buf[6] == '1');	/* ELF executable segments */
448 		assert(buf[7] == ' ');
449 		assert(buf[8] == '0');
450 		assert(buf[9] == ' ');
451 		assert(buf[10] == '0');	/* ->data_vm + ->stack_vm */
452 		assert(buf[11] == ' ');
453 		assert(buf[12] == '0');
454 		assert(buf[13] == '\n');
455 	}
456 
457 	return 0;
458 }
459 #else
main(void)460 int main(void)
461 {
462 	return 4;
463 }
464 #endif
465