Re: [PATCH] io_uring: Fix NULL pointer dereference in io_sq_wq_submit_work()
From: Jens Axboe <axboe@kernel.dk>
Date: 2020-09-01 03:39:07
Also in:
linux-fsdevel, lkml
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?
quoted hunk
@@ -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