From: Jens Axboe axboe@kernel.dk
[ upstream commmit 61bc84c4008812d784c398cfb54118c1ba396dfc ]
When the ring is exiting, as part of the shutdown, poll requests are removed. But io_poll_remove_all() does not remove entries when finding them, and since completions are done out-of-band, we can find and remove the same entry multiple times.
We do guard the poll execution by poll ownership, but that does not exclude us from reissuing a new one once the previous removal ownership goes away.
This can race with poll execution as well, where we then end up seeing req->apoll be NULL because a previous task_work requeue finished the request.
Remove the poll entry when we find it and get ownership of it. This prevents multiple invocations from finding it.
Fixes: aa43477b0402 ("io_uring: poll rework") Reported-by: Dylan Yudaken dylany@fb.com Signed-off-by: Jens Axboe axboe@kernel.dk [pavel: backport] Signed-off-by: Pavel Begunkov asml.silence@gmail.com --- fs/io_uring.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c index c4d34b4e8fb6..4ebc47ebb77a 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -5714,6 +5714,7 @@ static bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk, list = &ctx->cancel_hash[i]; hlist_for_each_entry_safe(req, tmp, list, hash_node) { if (io_match_task_safe(req, tsk, cancel_all)) { + hlist_del_init(&req->hash_node); io_poll_cancel_req(req); found = true; }