From c33880aaddbbab1ccf36f4457ed1090621f2e39a Mon Sep 17 00:00:00 2001
From: Kirill Korotaev <dev@sw.ru>
Date: Tue, 24 May 2005 19:29:47 -0700
Subject: [PATCH] sigkill priority fix

If SIGKILL does not have priority, we cannot instantly kill task before it
makes some unexpected job.  It can be critical, but we were unable to
reproduce this easily until Heiko Carstens <Heiko.Carstens@de.ibm.com>
reported this problem on LKML.

Signed-Off-By: Kirill Korotaev <dev@sw.ru>
Signed-Off-By: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
 kernel/signal.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 8f3debc77c5b..b3c24c732c5a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -522,7 +522,16 @@ static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
 {
 	int sig = 0;
 
-	sig = next_signal(pending, mask);
+	/* SIGKILL must have priority, otherwise it is quite easy
+	 * to create an unkillable process, sending sig < SIGKILL
+	 * to self */
+	if (unlikely(sigismember(&pending->signal, SIGKILL))) {
+		if (!sigismember(mask, SIGKILL))
+			sig = SIGKILL;
+	}
+
+	if (likely(!sig))
+		sig = next_signal(pending, mask);
 	if (sig) {
 		if (current->notifier) {
 			if (sigismember(current->notifier_mask, sig)) {
-- 
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