block: Fix NULL dereference on empty drive error

blk_error_action() sends a BLOCK_IO_ERROR QMP event which includes the
node name of its root node. If the BlockBackend represents an empty
drive, there is no root node, so we should not try to access its node
name. Make the field optional in the event and include it only when
the BlockBackend isn't empty.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

diff --git a/block/block-backend.c b/block/block-backend.c
index a775a3dd2f7342741be558c1005cd6952ceb1fc8..a4421252f8524630ceecca2cd5c54a811f47a446 100644 (file)
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1615,10 +1615,11 @@ static void send_qmp_error_event(BlockBackend *blk,
                                  bool is_read, int error)
 {
     IoOperationType optype;
+    BlockDriverState *bs = blk_bs(blk);
 
     optype = is_read ? IO_OPERATION_TYPE_READ : IO_OPERATION_TYPE_WRITE;
-    qapi_event_send_block_io_error(blk_name(blk),
-                                   bdrv_get_node_name(blk_bs(blk)), optype,
+    qapi_event_send_block_io_error(blk_name(blk), !!bs,
+                                   bs ? bdrv_get_node_name(bs) : NULL, optype,
                                    action, blk_iostatus_is_enabled(blk),
                                    error == ENOSPC, strerror(error),
                                    &error_abort);

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 5c5921bfb707007b53fb134c2d6bb31a643df0f9..00475f08d4e077e45261901abb1085ab9253810e 100644 (file)
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3676,7 +3676,8 @@
 #
 # @node-name: node name. Note that errors may be reported for the root node
 #             that is directly attached to a guest device rather than for the
-#             node where the error occurred. (Since: 2.8)
+#             node where the error occurred. The node name is not present if
+#             the drive is empty. (Since: 2.8)
 #
 # @operation: I/O operation
 #
@@ -3707,7 +3708,8 @@
 #
 ##
 { 'event': 'BLOCK_IO_ERROR',
-  'data': { 'device': 'str', 'node-name': 'str', 'operation': 'IoOperationType',
+  'data': { 'device': 'str', '*node-name': 'str',
+            'operation': 'IoOperationType',
             'action': 'BlockErrorAction', '*nospace': 'bool',
             'reason': 'str' } }