Re: [PATCH 1/2] io_uring: fail cancellation for EXITING tasks

[Pavel Begunkov <asml.silence@gmail.com>]

On 11/26/21 14:38, Pavel Begunkov wrote:
> We need original task's context to do cancellations, so if it's dying
> and the callback is executed in a fallback mode, fail the cancellation
> attempt.

Fixes: 89b263f6d56e6 ("io_uring: run linked timeouts from task_work")
Cc: stable@kernel.org # 5.15+

> 
> Reported-by: syzbot+ab0cfe96c2b3cd1c1153@syzkaller.appspotmail.com
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>   fs/io_uring.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index a4c508a1e0cf..7dd112d44adf 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -6882,10 +6882,11 @@ static inline struct file *io_file_get(struct io_ring_ctx *ctx,
>   static void io_req_task_link_timeout(struct io_kiocb *req, bool *locked)
>   {
>   	struct io_kiocb *prev = req->timeout.prev;
> -	int ret;
> +	int ret = -ENOENT;
>   
>   	if (prev) {
> -		ret = io_try_cancel_userdata(req, prev->user_data);
> +		if (!(req->task->flags & PF_EXITING))
> +			ret = io_try_cancel_userdata(req, prev->user_data);
>   		io_req_complete_post(req, ret ?: -ETIME, 0);
>   		io_put_req(prev);
>   	} else {
> 

-- 
Pavel Begunkov