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
  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  */
  19 static 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
  25 static 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
  31 void __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 }