ipc/sem.c: prevent queue.status tearing in semop

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>

diff --git a/ipc/sem.c b/ipc/sem.c
index 5af1943ad782b415a3dd331161e9b2ecccf89210..76e95e4f3aa284f6ded3962b3055233ea533add8 100644 (file)
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2118,7 +2118,7 @@ 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);