On 03.05.21 13:51, Vladimir Sementsov-Ogievskiy wrote:
03.05.2021 14:49, Max Reitz wrote:
On 03.05.21 13:05, Kevin Wolf wrote:
The error path needs to call tran_finalize(), too.

Fixes: CID 1452773
Fixes: 548a74c0dbc858edd1a7ee3045b5f2fe710bd8b1
Signed-off-by: Kevin Wolf <kw...@redhat.com>
---
  block.c | 7 ++++---
  1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/block.c b/block.c
index 874c22c43e..5c0ced6238 100644
--- a/block.c
+++ b/block.c
@@ -2918,13 +2918,14 @@ BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,                                      child_role, perm, shared_perm, opaque,
                                     &child, tran, errp);
      if (ret < 0) {
-        bdrv_unref(child_bs);
-        return NULL;
+        assert(child == NULL);
+        goto out;
      }
      ret = bdrv_refresh_perms(child_bs, errp);
-    tran_finalize(tran, ret);
+out:
+    tran_finalize(tran, ret);
      bdrv_unref(child_bs);
      return child;

Looks OK, so:

Reviewed-by: Max Reitz <mre...@redhat.com>

However, the function’s description says that it will return NULL on error.  But if bdrv_refresh_perms() fails, it will still return a non-NULL child.  Is that right?


No, it's reset to NULL on transaction abort, so code is correct. It's not obvious, and I've added a comment and assertion in my version of this fix "[PATCH 1/6] block: fix leak of tran in bdrv_root_attach_child"

The fact that the transaction keeps the pointer to this local variable around is a bit horrifying, but well.

Max


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