linux-kernel - [PATCH 3.19.y-ckt 097/102] net: pktgen: fix race between pktgen_thread_worker() and kthread

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Message-Id: <1442944358-1248-98-git-send-email-kamal@canonical.com>
Date:	Tue, 22 Sep 2015 10:52:33 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Oleg Nesterov <oleg@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 097/102] net: pktgen: fix race between pktgen_thread_worker() and kthread_stop()

3.19.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oleg Nesterov <oleg@...hat.com>

[ Upstream commit fecdf8be2d91e04b0a9a4f79ff06499a36f5d14f ]

pktgen_thread_worker() is obviously racy, kthread_stop() can come
between the kthread_should_stop() check and set_current_state().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reported-by: Jan Stancek <jstancek@...hat.com>
Reported-by: Marcelo Leitner <mleitner@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 net/core/pktgen.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index de4dc84..0fab2c4 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3493,8 +3493,10 @@ static int pktgen_thread_worker(void *arg)
 	pktgen_rem_thread(t);
 
 	/* Wait for kthread_stop */
-	while (!kthread_should_stop()) {
+	for (;;) {
 		set_current_state(TASK_INTERRUPTIBLE);
+		if (kthread_should_stop())
+			break;
 		schedule();
 	}
 	__set_current_state(TASK_RUNNING);
-- 
1.9.1

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