From: Pavel Begunkov asml.silence@gmail.com
commit 7fdbc5f014c3f71bc44673a2d6c5bb2d12d45f25 upstream.
When we post a CQE we wake all ring pollers as it normally should be. However, if a CQE was generated by a multishot poll request targeting its own ring, it'll wake that request up, which will make it to post a new CQE, which will wake the request and so on until it exhausts all CQ entries.
Don't allow multishot polling io_uring files but downgrade them to oneshots, which was always stated as a correct behaviour that the userspace should check for.
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/3124038c0e7474d427538c2d915335ec28c92d21.166878572... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/poll.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -244,6 +244,8 @@ static int io_poll_check_events(struct i continue; if (req->apoll_events & EPOLLONESHOT) return IOU_POLL_DONE; + if (io_is_uring_fops(req->file)) + return IOU_POLL_DONE;
/* multishot, just fill a CQE and proceed */ if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {