linux-kernel - [PATCH 5.12 031/292] io_uring: fix link timeout refs

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Message-Id: <20210719144943.553226991@linuxfoundation.org>
Date:   Mon, 19 Jul 2021 16:51:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+a2910119328ce8e7996f@...kaller.appspotmail.com,
        Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.12 031/292] io_uring: fix link timeout refs

From: Pavel Begunkov <asml.silence@...il.com>

commit a298232ee6b9a1d5d732aa497ff8be0d45b5bd82 upstream.

WARNING: CPU: 0 PID: 10242 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Call Trace:
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 io_put_req fs/io_uring.c:2140 [inline]
 io_queue_linked_timeout fs/io_uring.c:6300 [inline]
 __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354
 io_submit_sqe fs/io_uring.c:6534 [inline]
 io_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660
 __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]
 __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182

io_link_timeout_fn() should put only one reference of the linked timeout
request, however in case of racing with the master request's completion
first io_req_complete() puts one and then io_put_req_deferred() is
called.

Cc: stable@...r.kernel.org # 5.12+
Fixes: 9ae1f8dd372e0 ("io_uring: fix inconsistent lock state")
Reported-by: syzbot+a2910119328ce8e7996f@...kaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
Link: https://lore.kernel.org/r/ff51018ff29de5ffa76f09273ef48cb24c720368.1620417627.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/io_uring.c |    1 -
 1 file changed, 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6307,7 +6307,6 @@ static enum hrtimer_restart io_link_time
 	} else {
 		io_req_complete_post(req, -ETIME, 0);
 	}
-	io_put_req_deferred(req, 1);
 	return HRTIMER_NORESTART;
 }