linux-hardened/kernel/seccomp.c
Andrea Arcangeli cf99abace7 make seccomp zerocost in schedule
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>
2007-07-16 09:05:50 -07:00

85 lines
1.6 KiB
C

/*
* 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;
}