linux/kernel/seccomp.c
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   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