From 46fee9ab02cb24979bbe07631fc3ae95ae08aa3e Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Tue, 20 Jul 2021 10:50:44 +0100 Subject: [PATCH] io_uring: remove double poll entry on arm failure __io_queue_proc() can enqueue both poll entries and still fail afterwards, so the callers trying to cancel it should also try to remove the second poll entry (if any). For example, it may leave the request alive referencing a io_uring context but not accessible for cancellation: [ 282.599913][ T1620] task:iou-sqp-23145 state:D stack:28720 pid:23155 ppid: 8844 flags:0x00004004 [ 282.609927][ T1620] Call Trace: [ 282.613711][ T1620] __schedule+0x93a/0x26f0 [ 282.634647][ T1620] schedule+0xd3/0x270 [ 282.638874][ T1620] io_uring_cancel_generic+0x54d/0x890 [ 282.660346][ T1620] io_sq_thread+0xaac/0x1250 [ 282.696394][ T1620] ret_from_fork+0x1f/0x30 Cc: stable@vger.kernel.org Fixes: 18bceab101add ("io_uring: allow POLL_ADD with double poll_wait() users") Reported-and-tested-by: syzbot+ac957324022b7132accf@syzkaller.appspotmail.com Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/0ec1228fc5eda4cb524eeda857da8efdc43c331c.1626774457.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- fs/io_uring.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/io_uring.c b/fs/io_uring.c index 6668902cf50c..6486b54a0f62 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5113,6 +5113,8 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req, ipt->error = -EINVAL; spin_lock_irq(&ctx->completion_lock); + if (ipt->error) + io_poll_remove_double(req); if (likely(poll->head)) { spin_lock(&poll->head->lock); if (unlikely(list_empty(&poll->wait.entry))) { -- 2.20.1