David Howells 2ed147f015 watch_queue: Fix lack of barrier/sync/lock between post and read
There's nothing to synchronise post_one_notification() versus
pipe_read().  Whilst posting is done under pipe->rd_wait.lock, the
reader only takes pipe->mutex which cannot bar notification posting as
that may need to be made from contexts that cannot sleep.

Fix this by setting pipe->head with a barrier in post_one_notification()
and reading pipe->head with a barrier in pipe_read().

If that's not sufficient, the rd_wait.lock will need to be taken,
possibly in a ->confirm() op so that it only applies to notifications.
The lock would, however, have to be dropped before copy_page_to_iter()
is invoked.

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-03-11 10:17:13 -08:00
..
2022-01-30 22:13:37 +09:00
2022-01-22 08:33:37 +02:00
2021-08-19 09:02:55 +09:00
2022-03-06 12:19:36 -08:00
2021-11-09 10:02:51 -08:00
2021-10-25 19:11:50 -07:00
2022-01-12 11:11:34 -08:00
2021-12-03 18:44:06 +01:00
2022-02-11 11:36:32 -08:00
2021-11-03 09:23:25 -07:00
2022-02-04 00:12:22 -06:00
2022-02-02 10:14:31 -08:00
2022-02-09 09:56:57 -08:00
2022-01-22 08:33:38 +02:00
2022-02-01 11:23:02 -08:00
2022-01-10 11:48:37 -08:00
2021-08-19 09:02:55 +09:00
2022-02-26 09:53:19 -08:00
2021-12-17 16:56:35 +09:00
2022-01-22 08:33:34 +02:00
2021-11-17 09:26:09 +01:00
2022-03-01 11:31:37 -08:00
2022-01-12 13:45:12 -08:00
2022-01-22 08:33:35 +02:00
2022-01-21 16:07:21 +02:00
2022-02-04 00:12:22 -06:00
2022-01-22 08:33:38 +02:00
\n
2022-01-28 17:51:31 +02:00
2021-08-10 17:57:22 +02:00