linux-kernel - Re: [PATCH bpf-next v9 05/10] libbpf: Verify BTF Sorting

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAErzpmtHkYY1MWM+bNdOwNKxQTtWTcya22Bp68ZDOOSZtGgaXw@mail.gmail.com>
Date: Wed, 17 Dec 2025 11:19:56 +0800
From: Donglin Peng <dolinux.peng@...il.com>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: ast@...nel.org, andrii.nakryiko@...il.com, zhangxiaoqin@...omi.com, 
	ihor.solodrai@...ux.dev, linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	pengdonglin <pengdonglin@...omi.com>, Alan Maguire <alan.maguire@...cle.com>
Subject: Re: [PATCH bpf-next v9 05/10] libbpf: Verify BTF Sorting

On Wed, Dec 17, 2025 at 8:32 AM Eduard Zingerman <eddyz87@...il.com> wrote:
>
> On Mon, 2025-12-08 at 14:23 +0800, Donglin Peng wrote:
> > From: pengdonglin <pengdonglin@...omi.com>
> >
> > This patch checks whether the BTF is sorted by name in ascending
> > order. If sorted, binary search will be used when looking up types.
> >
> > Cc: Eduard Zingerman <eddyz87@...il.com>
> > Cc: Alexei Starovoitov <ast@...nel.org>
> > Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
> > Cc: Alan Maguire <alan.maguire@...cle.com>
> > Cc: Ihor Solodrai <ihor.solodrai@...ux.dev>
> > Cc: Xiaoqin Zhang <zhangxiaoqin@...omi.com>
> > Signed-off-by: pengdonglin <pengdonglin@...omi.com>
> > ---
> >  tools/lib/bpf/btf.c | 46 ++++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 45 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> > index 7f150c869bf6..a53d24704857 100644
> > --- a/tools/lib/bpf/btf.c
> > +++ b/tools/lib/bpf/btf.c
> > @@ -899,6 +899,49 @@ int btf__resolve_type(const struct btf *btf, __u32 type_id)
> >       return type_id;
> >  }
> >
> > +/*
> > + * Assuming that types are sorted by name in ascending order.
> > + */
> > +static int btf_compare_type_names(const void *a, const void *b, void *priv)
>
> This can be declared as ...(u32 a, u32 b, struct btf *btf).

Thanks, I will fix it in the next version.

>
> > +{
> > +     struct btf *btf = (struct btf *)priv;
> > +     struct btf_type *ta = btf_type_by_id(btf, *(__u32 *)a);
> > +     struct btf_type *tb = btf_type_by_id(btf, *(__u32 *)b);
> > +     const char *na, *nb;
> > +
> > +     na = btf__str_by_offset(btf, ta->name_off);
> > +     nb = btf__str_by_offset(btf, tb->name_off);
> > +     return strcmp(na, nb);
> > +}
> > +
> > +static void btf_check_sorted(struct btf *btf)
> > +{
> > +     const struct btf_type *t;
> > +     int i, k = 0, n;
> > +     __u32 sorted_start_id = 0;
> > +
> > +     if (btf->nr_types < 2)
> > +             return;
> > +
> > +     n = btf__type_cnt(btf) - 1;
> > +     for (i = btf->start_id; i < n; i++) {
> > +             k = i + 1;
> > +             if (btf_compare_type_names(&i, &k, btf) > 0)
> > +                     return;
> > +             t = btf_type_by_id(btf, i);
> > +             if (sorted_start_id == 0 &&
> > +                     !str_is_empty(btf__str_by_offset(btf, t->name_off)))
>                 ^^^^^^^^
> Nit: broken indentation.

Thanks, I will fix it.

>
> > +                     sorted_start_id = i;
> > +     }
> > +
> > +     t = btf_type_by_id(btf, k);
>
> Nit: please use 'n' instead of 'k'.

Thanks, I agree, although k equals n at this point.

>      Maybe just change condition in the loop and avoid the second part?
>      E.g.:
>
>        n = btf__type_cnt(btf);
>        for (...) {
>          ...
>          if (k < n && btf_compare_type_names(a: &i, b: &k, priv: btf) > 0)
>            return;
>          ...
>        }
>
>      A bit shorter/simpler this way.

Great, I agree and will fix it in the next version.

>
> > +     if (sorted_start_id == 0 &&
> > +             !str_is_empty(btf__str_by_offset(btf, t->name_off)))
> > +             sorted_start_id = k;
> > +     if (sorted_start_id)
> > +             btf->sorted_start_id = sorted_start_id;
> > +}
> > +
> >  static __s32 btf_find_by_name_bsearch(const struct btf *btf, const char *name,
> >                                               __s32 start_id, __s32 end_id)
> >  {
> > @@ -935,7 +978,7 @@ static __s32 btf_find_by_name_kind(const struct btf *btf, int start_id,
> >
> >       if (start_id < btf->start_id) {
> >               idx = btf_find_by_name_kind(btf->base_btf, start_id,
> > -                     type_name, kind);
> > +                                         type_name, kind);
>
> Nit: shouldn't be in this patch.

Thanks, I will fix it in the next version.

>
> >               if (idx >= 0)
> >                       return idx;
> >               start_id = btf->start_id;
> > @@ -1147,6 +1190,7 @@ static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf, b
> >       err = err ?: btf_sanity_check(btf);
> >       if (err)
> >               goto done;
> > +     btf_check_sorted(btf);
> >
> >  done:
> >       if (err) {
>