Messages in this thread | | | Subject | Re: [PATCH] io_uring: Fix NULL pointer dereference in io_sq_wq_submit_work() | From | Jens Axboe <> | Date | Mon, 31 Aug 2020 21:38:59 -0600 |
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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
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