per-zone and reclaim enhancements for memory controller: modifies vmscan.c for isolat...
[linux-2.6.git] / kernel / seccomp.c
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/seccomp.h>
10 #include <linux/sched.h>
11
12 /* #define SECCOMP_DEBUG 1 */
13 #define NR_SECCOMP_MODES 1
14
15 /*
16  * Secure computing mode 1 allows only read/write/exit/sigreturn.
17  * To be fully secure this must be combined with rlimit
18  * to limit the stack allocations too.
19  */
20 static int mode1_syscalls[] = {
21         __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
22         0, /* null terminated */
23 };
24
25 #ifdef TIF_32BIT
26 static int mode1_syscalls_32[] = {
27         __NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
28         0, /* null terminated */
29 };
30 #endif
31
32 void __secure_computing(int this_syscall)
33 {
34         int mode = current->seccomp.mode;
35         int * syscall;
36
37         switch (mode) {
38         case 1:
39                 syscall = mode1_syscalls;
40 #ifdef TIF_32BIT
41                 if (test_thread_flag(TIF_32BIT))
42                         syscall = mode1_syscalls_32;
43 #endif
44                 do {
45                         if (*syscall == this_syscall)
46                                 return;
47                 } while (*++syscall);
48                 break;
49         default:
50                 BUG();
51         }
52
53 #ifdef SECCOMP_DEBUG
54         dump_stack();
55 #endif
56         do_exit(SIGKILL);
57 }
58
59 long prctl_get_seccomp(void)
60 {
61         return current->seccomp.mode;
62 }
63
64 long prctl_set_seccomp(unsigned long seccomp_mode)
65 {
66         long ret;
67
68         /* can set it only once to be even more secure */
69         ret = -EPERM;
70         if (unlikely(current->seccomp.mode))
71                 goto out;
72
73         ret = -EINVAL;
74         if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
75                 current->seccomp.mode = seccomp_mode;
76                 set_thread_flag(TIF_SECCOMP);
77 #ifdef TIF_NOTSC
78                 disable_TSC();
79 #endif
80                 ret = 0;
81         }
82
83  out:
84         return ret;
85 }