[PATCH] Allow rt_sigqueueinfo and rt_tgsigqueueinfo to use si_code == SI_ASYNCIO

[Roland Dreier <roland@kernel.org>]

From: Roland Dreier <roland@purestorage.com>

Commit da48524eb206 ("Prevent rt_sigqueueinfo and rt_tgsigqueueinfo
from spoofing the signal code") made the check on si_code too strict:
glibc's aio implementation wants to queue signals with SI_ASYNCIO, and
indeed glibc's tst-aio4 fails with the patched kernel.

Fix this by loosening the new check to allow SI_ASYNCIO as well.

Reported-by: Klaus Dittrich <kladit@arcor.de>
Signed-off-by: Roland Dreier <roland@purestorage.com>
---
 kernel/signal.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 324eff5..b2bfa3a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -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 != SI_QUEUE && info.si_code != SI_ASYNCIO) {
 		/* 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 != SI_QUEUE && info->si_code != SI_ASYNCIO) {
 		/* We used to allow any < 0 si_code */
 		WARN_ON_ONCE(info->si_code < 0);
 		return -EPERM;