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

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Message-ID: <598909D8.5060202@iogearbox.net>
Date:   Tue, 08 Aug 2017 02:46:16 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Edward Cree <ecree@...arflare.com>, davem@...emloft.net
CC:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alexei Starovoitov <ast@...com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        iovisor-dev <iovisor-dev@...ts.iovisor.org>
Subject: Re: [PATCH v5 net-next 00/12] bpf: rewrite value tracking in verifier

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@...earbox.net>