From 92c159863d8afefa9ca25a180feba6bff11c2be5 Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso <dave@stgolabs.net>
Date: Thu, 26 Jul 2018 16:37:19 -0700
Subject: [PATCH] ipc/sem.c: prevent queue.status tearing in semop

[ Upstream commit f075faa300acc4f6301e348acde0a4580ed5f77c ]

In order for load/store tearing prevention to work, _all_ accesses to
the variable in question need to be done around READ and WRITE_ONCE()
macros.  Ensure everyone does so for q->status variable for
semtimedop().

Link: http://lkml.kernel.org/r/20180717052654.676-1-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 ipc/sem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index b2698ebdcb31..d6dd2dc9ddad 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2041,7 +2041,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,
 	}
 
 	do {
-		queue.status = -EINTR;
+		WRITE_ONCE(queue.status, -EINTR);
 		queue.sleeper = current;
 
 		__set_current_state(TASK_INTERRUPTIBLE);