From: Pavel Begunkov <asml.silence@xxxxxxxxx> commit 539bcb57da2f58886d7d5c17134236b0ec9cd15d upstream. We may never try to process a poll wake and its mask if there was multiple wake ups racing for queueing up a tw. Force io_poll_check_events() to update the mask by vfs_poll(). Cc: stable@xxxxxxxxxxxxxxx Fixes: aa43477b04025 ("io_uring: poll rework") Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> Link: https://lore.kernel.org/r/00344d60f8b18907171178d7cf598de71d127b0b.1668710222.git.asml.silence@xxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- io_uring/poll.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -226,6 +226,13 @@ static int io_poll_check_events(struct i return IOU_POLL_DONE; if (v & IO_POLL_CANCEL_FLAG) return -ECANCELED; + /* + * cqe.res contains only events of the first wake up + * and all others are be lost. Redo vfs_poll() to get + * up to date state. + */ + if ((v & IO_POLL_REF_MASK) != 1) + req->cqe.res = 0; /* the mask was stashed in __io_poll_execute */ if (!req->cqe.res) {