From 544d163d659d45a206d8929370d5a2984e546cb7 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Thu, 12 Jan 2023 13:08:56 +0000 Subject: io_uring: lock overflowing for IOPOLL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit syzbot reports an issue with overflow filling for IOPOLL: WARNING: CPU: 0 PID: 28 at io_uring/io_uring.c:734 io_cqring_event_overflow+0x1c0/0x230 io_uring/io_uring.c:734 CPU: 0 PID: 28 Comm: kworker/u4:1 Not tainted 6.2.0-rc3-syzkaller-16369-g358a161a6a9e #0 Workqueue: events_unbound io_ring_exit_work Call trace:  io_cqring_event_overflow+0x1c0/0x230 io_uring/io_uring.c:734  io_req_cqe_overflow+0x5c/0x70 io_uring/io_uring.c:773  io_fill_cqe_req io_uring/io_uring.h:168 [inline]  io_do_iopoll+0x474/0x62c io_uring/rw.c:1065  io_iopoll_try_reap_events+0x6c/0x108 io_uring/io_uring.c:1513  io_uring_try_cancel_requests+0x13c/0x258 io_uring/io_uring.c:3056  io_ring_exit_work+0xec/0x390 io_uring/io_uring.c:2869  process_one_work+0x2d8/0x504 kernel/workqueue.c:2289  worker_thread+0x340/0x610 kernel/workqueue.c:2436  kthread+0x12c/0x158 kernel/kthread.c:376  ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:863 There is no real problem for normal IOPOLL as flush is also called with uring_lock taken, but it's getting more complicated for IOPOLL|SQPOLL, for which __io_cqring_overflow_flush() happens from the CQ waiting path. Reported-and-tested-by: syzbot+6805087452d72929404e@syzkaller.appspotmail.com Cc: stable@vger.kernel.org # 5.10+ Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe --- io_uring/rw.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'io_uring/rw.c') diff --git a/io_uring/rw.c b/io_uring/rw.c index 8227af2e1c0f..9c3ddd46a1ad 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -1062,7 +1062,11 @@ int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin) continue; req->cqe.flags = io_put_kbuf(req, 0); - io_fill_cqe_req(req->ctx, req); + if (unlikely(!__io_fill_cqe_req(ctx, req))) { + spin_lock(&ctx->completion_lock); + io_req_cqe_overflow(req); + spin_unlock(&ctx->completion_lock); + } } if (unlikely(!nr_events)) -- cgit v1.2.1