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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Miklos Szeredi <mszeredi@redhat.com>,
        syzbot+ef054c4d3f64cd7f7cec@syzkaller.appspotmai
Subject: [PATCH 4.9 21/83] fuse: set FR_SENT while locked
Date:   Mon, 19 Nov 2018 17:28:47 +0100
Message-Id: <20181119162616.050781455@linuxfoundation.org>
In-Reply-To: <20181119162612.046511542@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@redhat.com>

commit 4c316f2f3ff315cb48efb7435621e5bfb81df96d upstream.

Otherwise fuse_dev_do_write() could come in and finish off the request, and
the set_bit(FR_SENT, ...) could trigger the WARN_ON(test_bit(FR_SENT, ...))
in request_end().

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reported-by: syzbot+ef054c4d3f64cd7f7cec@syzkaller.appspotmai
Fixes: 46c34a348b0a ("fuse: no fc->lock for pqueue parts")
Cc: <stable@vger.kernel.org> # v4.2
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/fuse/dev.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1311,8 +1311,8 @@ static ssize_t fuse_dev_do_read(struct f
 	}
 	list_move_tail(&req->list, &fpq->processing);
 	__fuse_get_request(req);
-	spin_unlock(&fpq->lock);
 	set_bit(FR_SENT, &req->flags);
+	spin_unlock(&fpq->lock);
 	/* matches barrier in request_wait_answer() */
 	smp_mb__after_atomic();
 	if (test_bit(FR_INTERRUPTED, &req->flags))