Eric Biggers 8dd7c46a59
wait: add wake_up_pollfree() ...
commit 42288cb44c4b5fff7653bc392b583a2b8bd6a8c0 upstream.
Several ->poll() implementations are special in that they use a
waitqueue whose lifetime is the current task, rather than the struct
file as is normally the case. This is okay for blocking polls, since a
blocking poll occurs within one task; however, non-blocking polls
require another solution. This solution is for the queue to be cleared
before it is freed, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'.
However, that has a bug: wake_up_poll() calls __wake_up() with
nr_exclusive=1. Therefore, if there are multiple "exclusive" waiters,
and the wakeup function for the first one returns a positive value, only
that one will be called. That's *not* what's needed for POLLFREE;
POLLFREE is special in that it really needs to wake up everyone.
Considering the three non-blocking poll systems:
- io_uring poll doesn't handle POLLFREE at all, so it is broken anyway.
- aio poll is unaffected, since it doesn't support exclusive waits.
However, that's fragile, as someone could add this feature later.
- epoll doesn't appear to be broken by this, since its wakeup function
returns 0 when it sees POLLFREE. But this is fragile.
Although there is a workaround (see epoll), it's better to define a
function which always sends POLLFREE to all waiters. Add such a
function. Also make it verify that the queue really becomes empty after
all waiters have been woken up.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org >
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com >
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org >
2021-12-14 10:18:06 +01:00
2021-03-17 16:43:42 +01:00
2020-04-02 15:28:16 +02:00
2020-04-29 16:31:24 +02:00
2020-01-27 14:50:42 +01:00
2021-08-08 08:54:28 +02:00
2021-06-16 11:55:01 +02:00
2021-04-14 08:22:36 +02:00
2020-10-01 13:14:28 +02:00
2020-11-05 11:08:34 +01:00
2021-03-30 14:37:02 +02:00
2020-01-27 14:51:19 +01:00
2021-09-22 11:47:49 +02:00
2020-06-30 23:17:12 -04:00
2020-01-23 08:21:39 +01:00
2021-12-08 08:50:11 +01:00
2021-05-22 10:59:30 +02:00
2021-09-22 11:47:47 +02:00
2021-08-12 13:19:42 +02:00
2021-05-07 10:49:25 +02:00
2020-01-09 10:19:01 +01:00
2021-08-08 08:54:29 +02:00
2021-08-08 08:54:29 +02:00
2020-08-19 08:15:05 +02:00
2020-06-25 15:33:02 +02:00
2021-03-04 09:39:30 +01:00
2020-04-29 16:31:17 +02:00
2021-09-22 11:47:59 +02:00
2021-03-30 14:37:02 +02:00
2020-04-23 10:30:12 +02:00
2020-12-30 11:25:39 +01:00
2020-09-09 19:04:31 +02:00
2021-09-26 13:39:48 +02:00
2020-07-22 09:32:00 +02:00
2020-07-22 09:32:00 +02:00
2021-01-30 13:32:11 +01:00
2021-03-24 11:07:31 +01:00
2020-12-30 11:25:40 +01:00
2021-01-23 15:49:55 +01:00
2021-10-06 15:31:17 +02:00
2021-05-26 11:48:35 +02:00
2021-11-26 11:36:02 +01:00
2019-12-31 16:36:22 +01:00
2021-08-08 08:54:30 +02:00
2021-10-06 15:31:28 +02:00
2020-11-05 11:08:35 +01:00
2020-10-01 13:14:28 +02:00
2020-04-17 10:48:45 +02:00
2021-03-04 09:39:57 +01:00
2021-08-26 08:36:41 -04:00
2021-01-23 15:49:55 +01:00
2020-02-24 08:34:44 +01:00
2021-03-11 14:05:02 +01:00
2020-09-03 11:24:23 +02:00
2021-10-27 09:53:13 +02:00
2020-06-25 15:33:02 +02:00
2020-02-11 04:34:08 -08:00
2021-04-07 12:48:50 +02:00
2021-12-08 08:50:13 +01:00
2021-11-26 11:35:59 +01:00
2020-10-14 10:31:21 +02:00
2021-12-08 08:50:13 +01:00
2021-09-22 11:47:56 +02:00
2021-09-22 11:47:56 +02:00
2020-11-05 11:08:35 +01:00
2021-01-30 13:32:12 +01:00
2021-03-11 14:04:59 +01:00
2021-12-14 10:18:03 +01:00
2020-11-05 11:08:54 +01:00
2020-01-04 19:13:32 +01:00
2021-07-11 12:49:27 +02:00
2021-09-22 11:48:09 +02:00
2020-08-11 15:32:33 +02:00
2020-09-23 12:10:59 +02:00
2021-05-22 10:59:40 +02:00
2021-03-04 09:39:59 +01:00
2020-05-10 10:30:12 +02:00
2020-01-12 12:17:25 +01:00
2021-03-30 14:37:00 +02:00
2020-07-22 09:32:00 +02:00
2020-03-18 07:14:11 +01:00
2021-08-26 08:36:39 -04:00
2021-02-03 23:23:26 +01:00
2020-02-28 16:38:59 +01:00
2020-07-29 10:16:57 +02:00
2020-05-10 10:30:11 +02:00
2020-04-17 10:48:41 +02:00
2021-05-22 10:59:50 +02:00
2021-12-08 08:50:11 +01:00
2021-03-04 09:39:59 +01:00
2021-08-26 08:36:40 -04:00
2020-02-28 16:38:50 +01:00
2020-07-16 08:17:26 +02:00
2021-01-09 13:43:48 +01:00
2021-03-04 09:39:42 +01:00
2020-04-23 10:30:24 +02:00
2021-03-04 09:39:44 +01:00
2020-06-22 09:05:15 +02:00
2020-10-14 10:31:26 +02:00
2021-12-08 08:50:12 +01:00
2021-02-07 14:48:38 +01:00
2021-09-26 13:39:46 +02:00
2020-04-29 16:31:19 +02:00
2021-11-26 11:35:57 +01:00
2020-01-04 19:13:15 +01:00
2020-02-24 08:34:46 +01:00
2021-09-22 11:47:57 +02:00
2020-09-09 19:04:28 +02:00
2021-11-26 11:35:56 +01:00
2021-04-28 13:16:51 +02:00
2021-10-09 14:11:03 +02:00
2020-02-11 04:34:18 -08:00
2021-09-22 11:48:12 +02:00
2020-01-29 16:43:27 +01:00
2021-07-11 12:49:28 +02:00
2021-07-11 12:49:26 +02:00
2020-10-07 08:00:08 +02:00
2020-07-29 10:16:52 +02:00
2021-05-22 10:59:23 +02:00
2021-08-26 08:36:41 -04:00
2021-03-30 14:37:02 +02:00
2021-06-30 08:48:18 -04:00
2021-07-20 16:16:01 +02:00
2021-12-08 08:50:14 +01:00
2020-11-18 19:18:44 +01:00
2020-11-18 19:18:44 +01:00
2020-12-02 08:48:07 +01:00
2021-07-20 16:16:11 +02:00
2020-10-01 13:14:41 +02:00
2020-10-07 08:00:08 +02:00
2020-04-13 10:45:06 +02:00
2020-04-17 10:48:45 +02:00
2021-12-08 08:50:11 +01:00
2021-01-06 14:45:00 +01:00
2021-09-03 09:58:00 +02:00
2020-10-29 09:55:15 +01:00
2020-10-30 10:38:20 +01:00
2021-08-08 08:54:30 +02:00
2020-03-25 08:06:13 +01:00
2021-07-11 12:49:30 +02:00
2020-06-22 09:05:25 +02:00
2020-04-17 10:48:46 +02:00
2021-11-26 11:36:19 +01:00
2020-04-23 10:30:20 +02:00
2020-02-11 04:34:11 -08:00
2021-06-10 13:24:08 +02:00
2020-03-18 07:14:17 +01:00
2020-01-27 14:50:26 +01:00
2020-05-20 08:18:45 +02:00
2020-01-17 19:46:55 +01:00
2020-01-04 19:13:35 +01:00
2021-07-20 16:15:46 +02:00
2020-07-22 09:32:13 +02:00
2021-01-12 20:10:17 +01:00
2021-06-30 08:48:19 -04:00
2020-01-04 19:12:53 +01:00
2020-08-07 09:36:21 +02:00
2020-02-24 08:34:46 +01:00
2021-07-11 12:49:28 +02:00
2021-11-26 11:36:14 +01:00
2020-01-27 14:50:37 +01:00
2021-12-14 10:18:04 +01:00
2021-10-17 10:19:49 +02:00
2021-11-26 11:35:56 +01:00
2020-04-02 15:28:22 +02:00
2020-12-30 11:26:01 +01:00
2020-10-01 13:14:30 +02:00
2020-06-22 09:05:03 +02:00
2020-01-27 14:51:05 +01:00
2021-12-08 08:50:13 +01:00
2021-09-22 11:48:11 +02:00
2021-05-22 10:59:39 +02:00
2021-06-30 08:48:18 -04:00
2021-03-17 16:43:51 +01:00
2021-02-13 13:51:15 +01:00
2020-04-17 10:48:43 +02:00
2020-04-23 10:30:19 +02:00
2020-01-27 14:50:22 +01:00
2021-03-07 12:19:01 +01:00
2020-07-31 18:37:48 +02:00
2021-03-24 11:07:37 +01:00
2020-11-18 19:18:40 +01:00
2021-10-09 14:11:04 +02:00
2020-01-23 08:21:32 +01:00
2020-12-30 11:26:01 +01:00
2021-07-20 16:15:42 +02:00
2021-05-22 10:59:31 +02:00
2020-12-11 13:25:01 +01:00
2021-03-30 14:36:58 +02:00
2020-09-09 19:04:29 +02:00
2021-03-24 11:07:34 +01:00
2021-11-26 11:36:22 +01:00
2020-10-07 08:00:05 +02:00
2020-04-29 16:31:27 +02:00
2020-04-02 15:28:23 +02:00
2021-12-14 10:18:06 +01:00
2020-08-11 15:32:34 +02:00
2021-03-07 12:19:01 +01:00
8dd7c46a59