Commit 243b422a authored Mar 28, 2011 by Roland Dreier Committed by Linus Torvalds Mar 28, 2011

Relax si_code check in rt_sigqueueinfo and rt_tgsigqueueinfo



Commit da48524e ("Prevent rt_sigqueueinfo and rt_tgsigqueueinfo
from spoofing the signal code") made the check on si_code too strict.
There are several legitimate places where glibc wants to queue a
negative si_code different from SI_QUEUE:

 - This was first noticed with glibc's aio implementation, which wants
   to queue a signal with si_code SI_ASYNCIO; the current kernel
   causes glibc's tst-aio4 test to fail because rt_sigqueueinfo()
   fails with EPERM.

 - Further examination of the glibc source shows that getaddrinfo_a()
   wants to use SI_ASYNCNL (which the kernel does not even define).
   The timer_create() fallback code wants to queue signals with SI_TIMER.

As suggested by Oleg Nesterov <oleg@redhat.com>, loosen the check to
forbid only the problematic SI_TKILL case.

Reported-by: Klaus Dittrich <kladit@arcor.de>
Acked-by: Julien Tinnes <jln@google.com>
Cc: <stable@kernel.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5847098c

kernel/signal.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -2437,7 +2437,7 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
		/* Not even root can pretend to send signals from the kernel.
		* Nor can they impersonate a kill()/tgkill(), which adds source info.
		*/
		if (info.si_code != SI_QUEUE) {
		if (info.si_code >= 0 \|\| info.si_code == SI_TKILL) {
		/* We used to allow any < 0 si_code */
		WARN_ON_ONCE(info.si_code < 0);
		return -EPERM;
		@@ -2457,7 +2457,7 @@ long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
		/* Not even root can pretend to send signals from the kernel.
		* Nor can they impersonate a kill()/tgkill(), which adds source info.
		*/
		if (info->si_code != SI_QUEUE) {
		if (info->si_code >= 0 \|\| info->si_code == SI_TKILL) {
		/* We used to allow any < 0 si_code */
		WARN_ON_ONCE(info->si_code < 0);
		return -EPERM;