Re: [Qemu-devel] [PATCH] migration/block-dirty-bitmap: fix Coverity CID1390625

[Vladimir Sementsov-Ogievskiy]

16.11.2018 17:29, Stefan Hajnoczi wrote:
> On Tue, Oct 16, 2018 at 04:20:18PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>> Theoretically possible that we finish the skipping loop with bs = NULL
>> and the following code will crash trying to dereference it. Fix that.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>> ---
>>   migration/block-dirty-bitmap.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
>> index 477826330c..6de808f95f 100644
>> --- a/migration/block-dirty-bitmap.c
>> +++ b/migration/block-dirty-bitmap.c
>> @@ -288,6 +288,10 @@ static int init_dirty_bitmap_migration(void)
>>               bs = backing_bs(bs);
>>           }
>>   
>> +        if (!bs || bs->implicit) {
> 
> Why is it necessary to check bs->implicit?
> 


to be sure, that it is not implicit, as previous loop may finish with implicit 
= true and bs!= NULL, if drv == NULL. (hmm, may be we want to check drv too?)

same thing is in bdrv_query_info, without any checks, and in 
bdrv_block_device_info with assert(bs).


-- 
Best regards,
Vladimir