/* * linux/kernel/seccomp.c * * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com> * * This defines a simple but solid secure-computing mode. */ #include <linux/seccomp.h> #include <linux/sched.h> /* #define SECCOMP_DEBUG 1 */ #define NR_SECCOMP_MODES 1 /* * Secure computing mode 1 allows only read/write/exit/sigreturn. * To be fully secure this must be combined with rlimit * to limit the stack allocations too. */ static int mode1_syscalls[] = { __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, 0, /* null terminated */ }; #ifdef TIF_32BIT static int mode1_syscalls_32[] = { __NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32, 0, /* null terminated */ }; #endif void __secure_computing(int this_syscall) { int mode = current->seccomp.mode; int * syscall; switch (mode) { case 1: syscall = mode1_syscalls; #ifdef TIF_32BIT if (test_thread_flag(TIF_32BIT)) syscall = mode1_syscalls_32; #endif do { if (*syscall == this_syscall) return; } while (*++syscall); break; default: BUG(); } #ifdef SECCOMP_DEBUG dump_stack(); #endif do_exit(SIGKILL); } long prctl_get_seccomp(void) { return current->seccomp.mode; } long prctl_set_seccomp(unsigned long seccomp_mode) { long ret; /* can set it only once to be even more secure */ ret = -EPERM; if (unlikely(current->seccomp.mode)) goto out; ret = -EINVAL; if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) { current->seccomp.mode = seccomp_mode; set_thread_flag(TIF_SECCOMP); #ifdef TIF_NOTSC disable_TSC(); #endif ret = 0; } out: return ret; }