io_uring: get an active ref_node from files_data

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>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index b205c1df3f743d4fc89e0bcc4c7bdc6b2266bc19..5cb194ca4fcec6a8f1c5887ee4e2aef25a5b8422 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6974,9 +6974,7 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
                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 = data->node;
        spin_unlock(&data->lock);
        if (ref_node)
                percpu_ref_kill(&ref_node->refs);