linux-kernel - [PATCH -next] ipc/sem: prevent queue.status tearing in semop

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Message-Id: <20180717052654.676-1-dave@stgolabs.net>
Date:   Mon, 16 Jul 2018 22:26:54 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     akpm@...ux-foundation.org
Cc:     manfred@...orfullife.com, dave@...olabs.net,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH -next] ipc/sem: prevent queue.status tearing in semop

In order for load/store tearing 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().

Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
---
 ipc/sem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 6cbbf34a44ac..ccab4e51d351 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2125,7 +2125,7 @@ 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);
-- 
2.16.4