| Message ID | 3124038c0e7474d427538c2d915335ec28c92d21.1668785722.git.asml.silence@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [for-6.1] io_uring: disallow self-propelled ring polling | expand |
On Fri, 18 Nov 2022 15:41:41 +0000, Pavel Begunkov wrote: > 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. > > [...] Applied, thanks! [1/1] io_uring: disallow self-propelled ring polling commit: 7fdbc5f014c3f71bc44673a2d6c5bb2d12d45f25 Best regards,
diff --git a/io_uring/poll.c b/io_uring/poll.c index f500506984ec..9fe31c1ebb7b 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -239,6 +239,8 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked) 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)) {
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> --- io_uring/poll.c | 2 ++ 1 file changed, 2 insertions(+)