Re: [PATCH v5 net-next 00/12] bpf: rewrite value tracking in verifier

[David Miller]

From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Date: Tue, 08 Aug 2017 02:46:16 +0200

> On 08/07/2017 04:21 PM, Edward Cree wrote:
>> This series simplifies alignment tracking, generalises bounds tracking
>> and
>>   fixes some bounds-tracking bugs in the BPF verifier.  Pointer
>>   arithmetic on
>>   packet pointers, stack pointers, map value pointers and context
>>   pointers has
>>   been unified, and bounds on these pointers are only checked when the
>>   pointer
>>   is dereferenced.
>> Operations on pointers which destroy all relation to the original
>> pointer
>>   (such as multiplies and shifts) are disallowed if
>>   !env->allow_ptr_leaks,
>>   otherwise they convert the pointer to an unknown scalar and feed it to
>>   the
>>   normal scalar arithmetic handling.
>> Pointer types have been unified with the corresponding
>> adjusted-pointer types
>>   where those existed (e.g. PTR_TO_MAP_VALUE[_ADJ] or FRAME_PTR vs
>>   PTR_TO_STACK); similarly, CONST_IMM and UNKNOWN_VALUE have been
>>   unified into
>>   SCALAR_VALUE.
>> Pointer types (except CONST_PTR_TO_MAP, PTR_TO_MAP_VALUE_OR_NULL and
>>   PTR_TO_PACKET_END, which do not allow arithmetic) have a 'fixed
>>   offset' and
>>   a 'variable offset'; the former is used when e.g. adding an immediate
>>   or a
>>   known-constant register, as long as it does not overflow.  Otherwise
>>   the
>>   latter is used, and any operation creating a new variable offset
>>   creates a
>>   new 'id' (and, for PTR_TO_PACKET, clears the 'range').
>> SCALAR_VALUEs use the 'variable offset' fields to track the range of
>> possible
>>   values; the 'fixed offset' should never be set on a scalar.
> 
> Been testing and reviewing the series over the last several days,
> looks
> reasonable to me as far as I can tell. Thanks for all the hard work on
> unifying this, Edward!
> 
> Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>

Series applied, thanks everyone!