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SubjectRe: [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
> 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 <>

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