From e0b245f8250719f43564b4e971584f9c6c32d571 Mon Sep 17 00:00:00 2001 From: Jiufei Xue Date: Fri, 14 Aug 2020 10:48:59 +0800 Subject: [PATCH 2049/2944] io_uring: hold 'ctx' reference around task_work queue + execute fix #29820404 commit 6d816e088c359866f9867057e04f244c608c42fe linux-block/io_uring-5.9 branch. We're holding the request reference, but we need to go one higher to ensure that the ctx remains valid after the request has finished. If the ring is closed with pending task_work inflight, and the given io_kiocb finishes sync during issue, then we need a reference to the ring itself around the task_work execution cycle. Cc: stable@vger.kernel.org # v5.7+ Reported-by: syzbot+9b260fc33297966f5a8e@syzkaller.appspotmail.com Signed-off-by: Jens Axboe Signed-off-by: Jiufei Xue Reviewed-by: Joseph Qi --- fs/io_uring.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/io_uring.c b/fs/io_uring.c index bda1e7c..afa7aa5 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4089,6 +4089,7 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll, tsk = req->task; req->result = mask; + percpu_ref_get(&req->ctx->refs); init_task_work(&req->task_work, func); /* * If this fails, then the task is exiting. When a task exits, the @@ -4174,6 +4175,7 @@ static void io_poll_task_handler(struct io_kiocb *req, struct io_kiocb **nxt) static void io_poll_task_func(struct callback_head *cb) { struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work); + struct io_ring_ctx *ctx = req->ctx; struct io_kiocb *nxt = NULL; io_poll_task_handler(req, &nxt); @@ -4184,6 +4186,7 @@ static void io_poll_task_func(struct callback_head *cb) __io_queue_sqe(nxt, NULL); mutex_unlock(&ctx->uring_lock); } + percpu_ref_put(&ctx->refs); } static int io_poll_double_wake(struct wait_queue_entry *wait, unsigned mode, @@ -4298,6 +4301,7 @@ static void io_async_task_func(struct callback_head *cb) if (io_poll_rewait(req, &apoll->poll)) { spin_unlock_irq(&ctx->completion_lock); + percpu_ref_put(&ctx->refs); return; } @@ -4336,6 +4340,7 @@ static void io_async_task_func(struct callback_head *cb) req_set_fail_links(req); io_double_put_req(req); } + percpu_ref_put(&ctx->refs); } static int io_async_wake(struct wait_queue_entry *wait, unsigned mode, int sync, -- 1.8.3.1