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
14/*
15 * Secure computing mode 1 allows only read/write/exit/sigreturn.
16 * To be fully secure this must be combined with rlimit
17 * to limit the stack allocations too.
18 */
19static int mode1_syscalls[] = {
20	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
21	0, /* null terminated */
22};
23
24#ifdef TIF_32BIT
25static int mode1_syscalls_32[] = {
26	__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
27	0, /* null terminated */
28};
29#endif
30
31void __secure_computing(int this_syscall)
32{
33	int mode = current->seccomp.mode;
34	int * syscall;
35
36	switch (mode) {
37	case 1:
38		syscall = mode1_syscalls;
39#ifdef TIF_32BIT
40		if (test_thread_flag(TIF_32BIT))
41			syscall = mode1_syscalls_32;
42#endif
43		do {
44			if (*syscall == this_syscall)
45				return;
46		} while (*++syscall);
47		break;
48	default:
49		BUG();
50	}
51
52#ifdef SECCOMP_DEBUG
53	dump_stack();
54#endif
55	do_exit(SIGKILL);
56}
57