linux-kernel - [PATCH 4.14 056/165] ipc/sem.c: prevent queue.status tearing in semop

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Date:   Mon,  3 Sep 2018 18:55:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>,
        Manfred Spraul <manfred@...orfullife.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.14 056/165] ipc/sem.c: prevent queue.status tearing in semop

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

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

From: Davidlohr Bueso <dave@...olabs.net>

[ 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@...e.de>
Cc: Manfred Spraul <manfred@...orfullife.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 ipc/sem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2041,7 +2041,7 @@ static long do_semtimedop(int semid, str
 	}
 
 	do {
-		queue.status = -EINTR;
+		WRITE_ONCE(queue.status, -EINTR);
 		queue.sleeper = current;
 
 		__set_current_state(TASK_INTERRUPTIBLE);