stream: Traverse graph after modification

bdrv_cor_filter_drop() modifies the block graph. That means that other parties can also modify the block graph before it returns. Therefore, we cannot assume that the result of a graph traversal we did before remains valid afterwards. We should thus fetch `base` and `unfiltered_base` afterwards instead of before. Signed-off-by: Hanna Reitz <[email protected]> Reviewed-by: Kevin Wolf <[email protected]> Reviewed-by: Vladimir Sementsov-Ogievskiy <[email protected]> Message-Id: <[email protected]> Signed-off-by: Kevin Wolf <[email protected]> Message-Id: <[email protected]> Signed-off-by: Hanna Reitz <[email protected]>
httoracle · Nov 16, 2021 · 8d3dd03 · 8d3dd03
1 parent 42f6c91
commit 8d3dd03
Showing 1 changed file with 5 additions and 2 deletions.
diff --git a/block/stream.c b/block/stream.c
@@ -54,15 +54,18 @@ static int stream_prepare(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
-    BlockDriverState *base = bdrv_filter_or_cow_bs(s->above_base);
-    BlockDriverState *unfiltered_base = bdrv_skip_filters(base);
+    BlockDriverState *base;
+    BlockDriverState *unfiltered_base;
     Error *local_err = NULL;
     int ret = 0;
 
     /* We should drop filter at this point, as filter hold the backing chain */
     bdrv_cor_filter_drop(s->cor_filter_bs);
     s->cor_filter_bs = NULL;
 
+    base = bdrv_filter_or_cow_bs(s->above_base);
+    unfiltered_base = bdrv_skip_filters(base);
+
     if (bdrv_cow_child(unfiltered_bs)) {
         const char *base_id = NULL, *base_fmt = NULL;
         if (unfiltered_base) {