Re: [PATCH 1/3] bpf: verifier: Accept dynptr mem as mem in helpers

[Daniel Rosenberg]

On Thu, Apr 6, 2023 at 3:13 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> +1
> All of the DYNPTR_TYPE_FLAG_MASK flags cannot appear in type == reg->type
> here.
> They are either dynamic flags inside bpf_dynptr_kern->size
> or in arg_type.
> Like in bpf_dynptr_from_mem_proto.

Looking at this a bit more, I believe this is to enforce packet
restrictions for DYNPTR_TYPE_SKB and DYNPTR_TYPE_XDP. When a helper
function alters a packet, dynptr slices of it are invalidated. If I
remove that annotation entirely, then the invalid_data_slice family of
tests fail. bpf_dynptr_from_mem_proto is fine since that's just local
dynptrs, which don't have any extra limitations.