Re: [Qemu-devel] [PATCH v3 1/3] block: resize backing file image during offline commit, if necessary

[Eric Blake]

On 01/23/2014 03:00 PM, Benoît Canet wrote:
> Le Thursday 23 Jan 2014 à 16:48:55 (-0500), Jeff Cody a écrit :
>> Currently, if an image file is logically larger than its backing file,
>> commiting it via 'qemu-img commit' will fail.

s/commiting/committing/


>> +    uint8_t *buf = NULL;
> 
> Why assign NULL to buf ? Is it related to the rest of the patch ?
> 
> Reviewed-by: Benoit Canet <address@hidden>
> 
>>      char filename[PATH_MAX];
>>  
>>      if (!drv)
>> @@ -1904,7 +1904,24 @@ int bdrv_commit(BlockDriverState *bs)
>>          }
>>      }
>>  
>> -    total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
>> +    length = bdrv_getlength(bs);
>> +    backing_length = bdrv_getlength(bs->backing_hd);
>> +
>> +    if (length < 0 || backing_length < 0) {
>> +        goto ro_cleanup;

Because this goto now reaches the ro_cleanup label with buf
uninitialized, if we don't assign NULL originally.

>> +    total_sectors = length >> BDRV_SECTOR_BITS;
>>      buf = g_malloc(COMMIT_BUF_SECTORS * BDRV_SECTOR_SIZE);

The old code only ever reached ro_cleanup after assigning buf, and
ro_cleanup blindly frees buf.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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