From: Pavel Begunkov asml.silence@gmail.com
commit 544d163d659d45a206d8929370d5a2984e546cb7 upstream.
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 asml.silence@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- io_uring/rw.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/io_uring/rw.c b/io_uring/rw.c index bb47cc4da713..6223472095d2 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -1055,7 +1055,11 @@ 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))