[PATCH 5.15 088/120] io_uring: update res mask in io_poll_check_events

Greg Kroah-Hartman
2022-12-05T19:39:43Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ upstream commit b98186aee22fa593bc8c6b2c5d839c2ee518bc8c ]

When io_poll_check_events() collides with someone attempting to queue a
task work, it'll spin for one more time. However, it'll continue to use
the mask from the first iteration instead of updating it. For example,
if the first wake up was a EPOLLIN and the second EPOLLOUT, the
userspace will not get EPOLLOUT in time.

Clear the mask for all subsequent iterations to force vfs_poll().

Cc: stable@vger.kernel.org
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2dac97e8f691231049cb259c4ae57e79e40b537c.1668710222.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/io_uring.c | 3 +++
1 file changed, 3 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5464,6 +5464,9 @@ static int io_poll_check_events(struct i
return 0;
}

+ /* force the next iteration to vfs_poll() */
+ req->result = 0;
+
/*
* Release all references, retry if someone tried to restart
* task_work while we were executing it.