cf99abace7
This follows a suggestion from Chuck Ebbert on how to make seccomp absolutely zerocost in schedule too. The only remaining footprint of seccomp is in terms of the bzImage size that becomes a few bytes (perhaps even a few kbytes) larger, measure it if you care in the embedded. Signed-off-by: Andrea Arcangeli <andrea@cpushare.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
85 lines
1.6 KiB
C
85 lines
1.6 KiB
C
/*
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* linux/kernel/seccomp.c
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*
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* Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
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*
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* This defines a simple but solid secure-computing mode.
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*/
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#include <linux/seccomp.h>
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#include <linux/sched.h>
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/* #define SECCOMP_DEBUG 1 */
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#define NR_SECCOMP_MODES 1
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/*
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* Secure computing mode 1 allows only read/write/exit/sigreturn.
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* To be fully secure this must be combined with rlimit
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* to limit the stack allocations too.
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*/
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static int mode1_syscalls[] = {
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__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
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0, /* null terminated */
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};
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#ifdef TIF_32BIT
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static int mode1_syscalls_32[] = {
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__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
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0, /* null terminated */
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};
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#endif
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void __secure_computing(int this_syscall)
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{
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int mode = current->seccomp.mode;
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int * syscall;
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switch (mode) {
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case 1:
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syscall = mode1_syscalls;
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#ifdef TIF_32BIT
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if (test_thread_flag(TIF_32BIT))
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syscall = mode1_syscalls_32;
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#endif
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do {
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if (*syscall == this_syscall)
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return;
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} while (*++syscall);
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break;
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default:
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BUG();
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}
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#ifdef SECCOMP_DEBUG
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dump_stack();
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#endif
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do_exit(SIGKILL);
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}
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long prctl_get_seccomp(void)
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{
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return current->seccomp.mode;
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}
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long prctl_set_seccomp(unsigned long seccomp_mode)
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{
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long ret;
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/* can set it only once to be even more secure */
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ret = -EPERM;
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if (unlikely(current->seccomp.mode))
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goto out;
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ret = -EINVAL;
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if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
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current->seccomp.mode = seccomp_mode;
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set_thread_flag(TIF_SECCOMP);
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#ifdef TIF_NOTSC
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disable_TSC();
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#endif
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ret = 0;
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}
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out:
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return ret;
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}
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