diff options
| author | Jens Axboe <axboe@kernel.dk> | 2023-01-20 15:08:21 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2023-01-20 15:11:54 -0700 |
| commit | 8caa03f10bf92cb8657408a6ece6a8a73f96ce13 (patch) | |
| tree | 4966ad5c97201debcb18607e0c6feeafeaa202de | |
| parent | 8579538c89e33ce78be2feb41e07489c8cbf8f31 (diff) | |
io_uring/poll: don't reissue in case of poll race on multishot request
A previous commit fixed a poll race that can occur, but it's only
applicable for multishot requests. For a multishot request, we can safely
ignore a spurious wakeup, as we never leave the waitqueue to begin with.
A blunt reissue of a multishot armed request can cause us to leak a
buffer, if they are ring provided. While this seems like a bug in itself,
it's not really defined behavior to reissue a multishot request directly.
It's less efficient to do so as well, and not required to rearm anything
like it is for singleshot poll requests.
Cc: stable@vger.kernel.org
Fixes: 6e5aedb9324a ("io_uring/poll: attempt request issue after racy poll wakeup")
Reported-and-tested-by: Olivier Langlois <olivier@trillion01.com>
Link: https://github.com/axboe/liburing/issues/778
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | io_uring/poll.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/io_uring/poll.c b/io_uring/poll.c index 32e5fc8365e6..2ac1366adbd7 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -283,8 +283,12 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked) * to the waitqueue, so if we get nothing back, we * should be safe and attempt a reissue. */ - if (unlikely(!req->cqe.res)) + if (unlikely(!req->cqe.res)) { + /* Multishot armed need not reissue */ + if (!(req->apoll_events & EPOLLONESHOT)) + continue; return IOU_POLL_REISSUE; + } } if (req->apoll_events & EPOLLONESHOT) return IOU_POLL_DONE; |