drbd: fix an invalid memory access caused by incorrect use of list iterator

The bug is here:
	idr_remove(&connection->peer_devices, vnr);

If the previous for_each_connection() don't exit early (no goto hit
inside the loop), the iterator 'connection' after the loop will be a
bogus pointer to an invalid structure object containing the HEAD
(&resource->connections). As a result, the use of 'connection' above
will lead to a invalid memory access (including a possible invalid free
as idr_remove could call free_layer).

The original intention should have been to remove all peer_devices,
but the following lines have already done the work. So just remove
this line and the unneeded label, to fix this bug.

Cc: stable@vger.kernel.org
Fixes: c06ece6ba6f1b ("drbd: Turn connection->volumes into connection->peer_devices")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Reviewed-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 9676a1d..d6dfa28 100644 (file)
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2773,12 +2773,12 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
 
        if (init_submitter(device)) {
                err = ERR_NOMEM;
-               goto out_idr_remove_vol;
+               goto out_idr_remove_from_resource;
        }
 
        err = add_disk(disk);
        if (err)
-               goto out_idr_remove_vol;
+               goto out_idr_remove_from_resource;
 
        /* inherit the connection state */
        device->state.conn = first_connection(resource)->cstate;
@@ -2792,8 +2792,6 @@ enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsig
        drbd_debugfs_device_add(device);
        return NO_ERROR;
 
-out_idr_remove_vol:
-       idr_remove(&connection->peer_devices, vnr);
 out_idr_remove_from_resource:
        for_each_connection(connection, resource) {
                peer_device = idr_remove(&connection->peer_devices, vnr);