io_uring/net: don't retry connect operation on EPOLLERR

If a socket is shutdown before the connection completes, POLLERR is set
in the poll mask. However, connect ignores this as it doesn't know, and
attempts the connection again. This may lead to a bogus -ETIMEDOUT
result, where it should have noticed the POLLERR and just returned
-ECONNRESET instead.

Have the poll logic check for whether or not POLLERR is set in the mask,
and if so, mark the request as failed. Then connect can appropriately
fail the request rather than retry it.

Reported-by: Sergey Galas <ssgalas@cloud.ru>
Cc: stable@vger.kernel.org
Link: axboe/liburing#1335
Fixes: 3fb1bd6 ("io_uring/net: handle -EINPROGRESS correct for IORING_OP_CONNECT")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/net.c

@@ -1710,6 +1710,11 @@ int io_connect(struct io_kiocb *req, unsigned int issue_flags)
 	int ret;
 	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
 
+	if (unlikely(req->flags & REQ_F_FAIL)) {
+		ret = -ECONNRESET;
+		goto out;
+	}
+
 	file_flags = force_nonblock ? O_NONBLOCK : 0;
 
 	ret = __sys_connect_file(req->file, &io->addr, connect->addr_len,

io_uring/poll.c

@@ -273,6 +273,8 @@ static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts)
 				return IOU_POLL_REISSUE;
 			}
 		}
+		if (unlikely(req->cqe.res & EPOLLERR))
+			req_set_fail(req);
 		if (req->apoll_events & EPOLLONESHOT)
 			return IOU_POLL_DONE;