[PULL,v2,01/13] stream: Traverse graph after modification

Commit Message

Hanna Czenczek Nov. 16, 2021, 1:06 p.m. UTC

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 <[e-mail]>
Reviewed-by: Kevin Wolf <[e-mail]>
Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Kevin Wolf <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Hanna Reitz <[e-mail]>
---
 block/stream.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

Patch

diff --git a/block/stream.c b/block/stream.c
index 97bee482dc..e45113aed6 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -54,8 +54,8 @@  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;
 
@@ -63,6 +63,9 @@  static int stream_prepare(Job *job)
     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) {