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

Davidlohr Bueso · torvalds · commit f075faa300ac · 2018-07-26T19:38:03.000-07:00
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
@@ -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);

Original file line number	Diff line number	Diff line change
`@@ -2118,7 +2118,7 @@ static long do_semtimedop(int semid, struct sembuf __user *tsops,`
`2118`	`2118`	`}`
`2119`	`2119`
`2120`	`2120`	`do {`
`2121`		`- queue.status = -EINTR;`
	`2121`	`+ WRITE_ONCE(queue.status, -EINTR);`
`2122`	`2122`	`queue.sleeper = current;`
`2123`	`2123`
`2124`	`2124`	`__set_current_state(TASK_INTERRUPTIBLE);`