On 8/31/20 7:54 PM, Xin Yin wrote:
> the commit <1c4404efcf2c0> ("<io_uring: make sure async workqueue
> is canceled on exit>") caused a crash in io_sq_wq_submit_work().
> when io_ring-wq get a req form async_list, which may not have been
> added to task_list. Then try to delete the req from task_list will caused
> a "NULL pointer dereference".
Hmm, do you have a reproducer for this?
> @@ -2356,9 +2358,11 @@ static void io_sq_wq_submit_work(struct work_struct
> *work)
> * running. We currently only allow this if the new request is sequential
> * to the previous one we punted.
> */
> -static bool io_add_to_prev_work(struct async_list *list, struct io_kiocb
> *req)
> +static bool io_add_to_prev_work(struct async_list *list, struct io_kiocb
> *req,
> + struct io_ring_ctx *ctx)
> {
> bool ret;
> + unsigned long flags;
>
> if (!list)
> return false;
> @@ -2378,6 +2382,13 @@ static bool io_add_to_prev_work(struct async_list
> *list, struct io_kiocb *req)
> list_del_init(&req->list);
> ret = false;
> }
> +
> + if (ret) {
> + spin_lock_irqsave(&ctx->task_lock, flags);
> + list_add(&req->task_list, &ctx->task_list);
> + req->work_task = NULL;
> + spin_unlock_irqrestore(&ctx->task_lock, flags);
> + }
> spin_unlock(&list->lock);
> return ret;
> }
> @@ -2454,7 +2465,7 @@ static int __io_queue_sqe(struct io_ring_ctx *ctx,
> struct io_kiocb *req,
> s->sqe = sqe_copy;
> memcpy(&req->submit, s, sizeof(*s));
> list = io_async_list_from_req(ctx, req);
> - if (!io_add_to_prev_work(list, req)) {
> + if (!io_add_to_prev_work(list, req, ctx)) {
> if (list)
> atomic_inc(&list->cnt);
> INIT_WORK(&req->work, io_sq_wq_submit_work);
>
ctx == req->ctx, so you should not need that change.
--
Jens Axboe
