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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, Pavel Begunkov <asml.silence@gmail.com>,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 5.9 001/152] io_uring: get an active ref_node from files_data
Date:   Tue,  1 Dec 2020 09:51:56 +0100
Message-Id: <20201201084711.858351374@linuxfoundation.org>
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From: Pavel Begunkov <asml.silence@gmail.com>

commit 1e5d770bb8a23dd01e28e92f4fb0b1093c8bdbe6 upstream.

An active ref_node always can be found in ctx->files_data, it's much
safer to get it this way instead of poking into files_data->ref_list.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/io_uring.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6854,9 +6854,8 @@ static int io_sqe_files_unregister(struc
 		return -ENXIO;
 
 	spin_lock(&data->lock);
-	if (!list_empty(&data->ref_list))
-		ref_node = list_first_entry(&data->ref_list,
-				struct fixed_file_ref_node, node);
+	ref_node = container_of(data->cur_refs, struct fixed_file_ref_node,
+				refs);
 	spin_unlock(&data->lock);
 	if (ref_node)
 		percpu_ref_kill(&ref_node->refs);