Re: [PATCH bpf-next v2 0/2] Use overflow.h helpers to check for overflows

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Jul 01, 2024 at 01:59:03PM +0800, Shung-Hsi Yu wrote:
> This patch set refactors kernel/bpf/verifier.c to use type-agnostic,
> generic overflow-check helpers defined in include/linux/overflow.h to
> check for addition and subtraction overflow, and drop the
> signed_*_overflows() helpers we currently have in kernel/bpf/verifier.c.
> There should be no functional change in how the verifier works.
> 
> The main motivation is to make future refactoring[1] easier.
> 
> While check_mul_overflow() also exists and could potentially replace what
> we have in scalar*_min_max_mul(), it does not help with refactoring and
> would either change how the verifier works (e.g. lifting restriction on
> umax<=U32_MAX and u32_max<=U16_MAX) or make the code slightly harder to
> read, so it is left for future endeavour.
> 
> Changes from v1 <https://lore.kernel.org/r/20240623070324.12634-1-shung-hsi.yu@suse.com>:
> - use pointers to values in dst_reg directly as the sum/diff pointer and
>   remove the else branch (Jiri)
> - change local variables to be dst_reg pointers instead of src_reg values
> - include comparison of generated assembly before & after the change
>   (Alexei)
> 
> 1: https://github.com/kernel-patches/bpf/pull/7205/commits

CI failed, but it looks like aws hiccup:
  https://github.com/kernel-patches/bpf/actions/runs/9739067425/job/26873810583

lgtm

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> 
> Shung-Hsi Yu (2):
>   bpf: use check_add_overflow() to check for addition overflows
>   bpf: use check_sub_overflow() to check for subtraction overflows
> 
>  kernel/bpf/verifier.c | 151 ++++++++++++------------------------------
>  1 file changed, 42 insertions(+), 109 deletions(-)
> 
> -- 
> 2.45.2
>