1 /*
2 * linux/kernel/seccomp.c
3 *
4 * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
5 *
6 * This defines a simple but solid secure-computing mode.
7 */
8
9 #include <linux/audit.h>
10 #include <linux/seccomp.h>
11 #include <linux/sched.h>
12 #include <linux/compat.h>
13
14 /* #define SECCOMP_DEBUG 1 */
15 #define NR_SECCOMP_MODES 1
16
17 /*
18 * Secure computing mode 1 allows only read/write/exit/sigreturn.
19 * To be fully secure this must be combined with rlimit
20 * to limit the stack allocations too.
21 */
22 static int mode1_syscalls[] = {
23 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
24 0, /* null terminated */
25 };
26
27 #ifdef CONFIG_COMPAT
28 static int mode1_syscalls_32[] = {
29 __NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
30 0, /* null terminated */
31 };
32 #endif
33
__secure_computing(int this_syscall)34 void __secure_computing(int this_syscall)
35 {
36 int mode = current->seccomp.mode;
37 int * syscall;
38
39 switch (mode) {
40 case 1:
41 syscall = mode1_syscalls;
42 #ifdef CONFIG_COMPAT
43 if (is_compat_task())
44 syscall = mode1_syscalls_32;
45 #endif
46 do {
47 if (*syscall == this_syscall)
48 return;
49 } while (*++syscall);
50 break;
51 default:
52 BUG();
53 }
54
55 #ifdef SECCOMP_DEBUG
56 dump_stack();
57 #endif
58 audit_seccomp(this_syscall);
59 do_exit(SIGKILL);
60 }
61
prctl_get_seccomp(void)62 long prctl_get_seccomp(void)
63 {
64 return current->seccomp.mode;
65 }
66
prctl_set_seccomp(unsigned long seccomp_mode)67 long prctl_set_seccomp(unsigned long seccomp_mode)
68 {
69 long ret;
70
71 /* can set it only once to be even more secure */
72 ret = -EPERM;
73 if (unlikely(current->seccomp.mode))
74 goto out;
75
76 ret = -EINVAL;
77 if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
78 current->seccomp.mode = seccomp_mode;
79 set_thread_flag(TIF_SECCOMP);
80 #ifdef TIF_NOTSC
81 disable_TSC();
82 #endif
83 ret = 0;
84 }
85
86 out:
87 return ret;
88 }
89