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 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 62 long prctl_get_seccomp(void) 63 { 64 return current->seccomp.mode; 65 } 66 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