| Message ID | 8997c26b-c498-166d-d130-2caca08a3abb@kernel.dk (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | io_uring/poll: don't reissue in case of poll race on multishot request | expand |
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;
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> ---