This is a note to let you know that I've just added the patch titled io_uring: fix race between poll completion and cancel_hash insertion to the 5.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: io_uring-fix-race-between-poll-completion-and-cancel.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 2463ccfa8ddbfb67c569038aae873daa937c4319 Author: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx> Date: Wed Sep 22 18:12:36 2021 +0800 io_uring: fix race between poll completion and cancel_hash insertion [ Upstream commit bd99c71bd14072ce2920f6d0c2fe43df072c653c ] If poll arming and poll completion runs in parallel, there maybe races. For instance, run io_poll_add in iowq and io_poll_task_func in original context, then: iowq original context io_poll_add vfs_poll (interruption happens tw queued to original context) io_poll_task_func generate cqe del from cancel_hash[] if !poll.done insert to cancel_hash[] The entry left in cancel_hash[], similar case for fast poll. Fix it by set poll.done = true when del from cancel_hash[]. Fixes: 5082620fb2ca ("io_uring: terminate multishot poll for CQ ring overflow") Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210922101238.7177-2-haoxu@xxxxxxxxxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/io_uring.c b/fs/io_uring.c index 754d59f734d8..27a1c813f1e1 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4968,10 +4968,8 @@ static bool io_poll_complete(struct io_kiocb *req, __poll_t mask) } if (req->poll.events & EPOLLONESHOT) flags = 0; - if (!io_cqring_fill_event(ctx, req->user_data, error, flags)) { - req->poll.done = true; + if (!io_cqring_fill_event(ctx, req->user_data, error, flags)) flags = 0; - } if (flags & IORING_CQE_F_MORE) ctx->cq_extra++; @@ -4993,6 +4991,7 @@ static void io_poll_task_func(struct io_kiocb *req) if (done) { io_poll_remove_double(req); hash_del(&req->hash_node); + req->poll.done = true; } else { req->result = 0; add_wait_queue(req->poll.head, &req->poll.wait); @@ -5126,6 +5125,7 @@ static void io_async_task_func(struct io_kiocb *req) hash_del(&req->hash_node); io_poll_remove_double(req); + apoll->poll.done = true; spin_unlock_irq(&ctx->completion_lock); if (!READ_ONCE(apoll->poll.canceled))