Re: [Qemu-devel] [PATCH v2 6/7] nbd-client: Stricter enforcing of structured reply spec

[Eric Blake <eblake@redhat.com>]

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On 11/09/2017 03:37 AM, Vladimir Sementsov-Ogievskiy wrote:
> 09.11.2017 00:57, Eric Blake wrote:
>> Ensure that the server is not sending unexpected chunk lengths
>> for either the NONE or the OFFSET_DATA chunk, nor unexpected
>> hole length for OFFSET_HOLE.  This will flag any server that
>> responds to a zero-length read with an OFFSET_DATA as broken,
> 
> or OFFSET_HOLE

True, even though our implementation was not doing that.  I can tweak
the commit message.

> 
>> even though we previously fixed our client to never be able to
>> send such a request over the wire.
>>
>> Signed-off-by: Eric Blake <eblake@redhat.com>
>> ---
>>   block/nbd-client.c | 12 +++++++++---
>>   1 file changed, 9 insertions(+), 3 deletions(-)
>>

>> @@ -281,7 +281,8 @@ static int
>> nbd_co_receive_offset_data_payload(NBDClientSession *s,
>>
>>       assert(nbd_reply_is_structured(&s->reply));
>>
>> -    if (chunk->length < sizeof(offset)) {
>> +    /* The NBD spec requires at least one byte of payload */
>> +    if (chunk->length <= sizeof(offset)) {
>>           error_setg(errp, "Protocol error: invalid payload for "
>>                            "NBD_REPLY_TYPE_OFFSET_DATA");
>>           return -EINVAL;
>> @@ -293,7 +294,7 @@ static int
>> nbd_co_receive_offset_data_payload(NBDClientSession *s,
>>       be64_to_cpus(&offset);
>>
>>       data_size = chunk->length - sizeof(offset);
>> -    if (offset < orig_offset || data_size > qiov->size ||
>> +    if (!data_size || offset < orig_offset || data_size > qiov->size ||
> 
> !data_size - always false here (because of previous check), and even if
> it could be zero it
> isn't correspond to error message.
> 
> without this, or with an assert instead:

I like the assert instead.

> 
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> 
> 

Thanks for the reviews; I'll queue this series onto my NBD tree with
your suggestions incorporated, and send a pull request for 2.11 shortly.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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