Re: [PATCH] af_packet: Allow for > 8 byte hardware addresses.

[ebiederm@xmission.com (Eric W. Biederman)]

"David S. Miller" <davem@davemloft.net> writes:

> From: ebiederm@xmission.com (Eric W. Biederman)
> Date: Sat, 10 Sep 2005 11:25:27 -0600
>
>> @@ -1315,11 +1340,16 @@ packet_setsockopt(struct socket *sock, i
>>  	case PACKET_ADD_MEMBERSHIP:	
>>  	case PACKET_DROP_MEMBERSHIP:
>>  	{
>> -		struct packet_mreq mreq;
>> -		if (optlen<sizeof(mreq))
>> +		struct packet_mreq_max mreq;
>> +		int len = optlen;
>> +		if (len < sizeof(struct packet_mreq))
>>  			return -EINVAL;
>> -		if (copy_from_user(&mreq,optval,sizeof(mreq)))
>> +		if (len > sizeof(mreq))
>> +			len = sizeof(mreq);
>> +		if (copy_from_user(&mreq,optval,len))
>>  			return -EFAULT;
>
> I would suggest memset()'ing out any packet_mreq_max structure,
> before copying a smaller amount of data into it, just to be
> safe.  Please check this out in all such possible uses in
> the patch.
>
> Thanks.

Ok.  For that specific case you have quoted the only instance.

In a practical sense it doesn't matter because halen determines
how many of the bytes we actually look at.  But if something
is buggy I can see the memset causing the bug to act in a
more deterministic fashion.

Updated patch will follow in a bit.

Eric