Re: [PATCH 1/2] block: Fix Transaction leak in bdrv_root_attach_child()

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

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 <kwolf@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 <mreitz@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"

-- 
Best regards,
Vladimir