On 1/14/23 2:51 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 6.1-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Here's this one.
--
Jens Axboe
From b800a0647421fc4c4aca538a9f0bc5bfceaece65 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
Date: Sat, 14 Jan 2023 08:41:33 -0700
Subject: [PATCH 1/2] io_uring: lock overflowing for IOPOLL
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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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@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # 5.10+
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
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))
--
2.39.0
