On Tue, Aug 04, 2020 at 11:27:55PM -0700, Andrii Nakryiko wrote:
SNIP
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index 7bacc2f56061..ba05b15ad599 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -4160,6 +4160,37 @@ int btf_struct_access(struct bpf_verifier_log *log,
> > return -EINVAL;
> > }
> >
> > +bool btf_struct_ids_match(struct bpf_verifier_log *log,
> > + int off, u32 id, u32 need_type_id)
> > +{
> > + const struct btf_type *type;
> > + int err;
> > +
> > + /* Are we already done? */
> > + if (need_type_id == id && off == 0)
> > + return true;
> > +
> > +again:
> > + type = btf_type_by_id(btf_vmlinux, id);
> > + if (!type)
> > + return false;
> > + err = btf_struct_walk(log, type, off, 1, &id);
>
> nit: this size=1 looks a bit artificial, seems like btf_struct_walk()
> will work with size==0 just as well, no?
right, it will work the same for 0 ... not sure why I put
originaly 1 byte for size.. probably got mixed up by some
condition in btf_struct_walk that I thought 0 wouldn't pass,
but it should work, I'll change it, it's less tricky
>
> > + if (err != WALK_STRUCT)
> > + return false;
> > +
> > + /* We found nested struct object. If it matches
> > + * the requested ID, we're done. Otherwise let's
> > + * continue the search with offset 0 in the new
> > + * type.
> > + */
> > + if (need_type_id != id) {
> > + off = 0;
> > + goto again;
> > + }
> > +
> > + return true;
> > +}
> > +
> > int btf_resolve_helper_id(struct bpf_verifier_log *log,
> > const struct bpf_func_proto *fn, int arg)
> > {
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index b6ccfce3bf4c..bb6ca19f282d 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -3960,16 +3960,21 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
> > goto err_type;
> > }
> > } else if (arg_type == ARG_PTR_TO_BTF_ID) {
> > + bool ids_match = false;
> > +
> > expected_type = PTR_TO_BTF_ID;
> > if (type != expected_type)
> > goto err_type;
> > if (!fn->check_btf_id) {
> > - if (reg->btf_id != meta->btf_id) {
> > - verbose(env, "Helper has type %s got %s in R%d\n",
> > - kernel_type_name(meta->btf_id),
> > - kernel_type_name(reg->btf_id), regno);
> > -
> > - return -EACCES;
> > + if (reg->btf_id != meta->btf_id || reg->off) {
>
> Will it ever succeed if reg->btf_id == meta->btf_id, but reg->off > 0?
> That would require recursively nested type, which is not possible,
> right? Or what am I missing? Is it just a simplification of the error
> handling path?
ok, I wanted to cover all possible cases, but did not realized this
one is not possible ;-) will revert it to previous version
thanks,
jirka
