lkml.org 
[lkml]   [2022]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] bpf/verifier: fix control flow issues in __reg64_bound_u32()
On Fri, Jul 29, 2022 at 10:15 AM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 7/28/22 10:49 PM, Zeng Jingxiang wrote:
> > From: Zeng Jingxiang <linuszeng@tencent.com>
> >
> > This greater-than-or-equal-to-zero comparison of an unsigned value
> > is always true. "a >= U32_MIN".
> > 1632 return a >= U32_MIN && a <= U32_MAX;
> >
> > Fixes: b9979db83401 ("bpf: Fix propagation of bounds from 64-bit min/max into 32-bit and var_off.")
> > Signed-off-by: Zeng Jingxiang <linuszeng@tencent.com>
> > ---
> > kernel/bpf/verifier.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 0efbac0fd126..dd67108fb1d7 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -1629,7 +1629,7 @@ static bool __reg64_bound_s32(s64 a)
> >
> > static bool __reg64_bound_u32(u64 a)
> > {
> > - return a >= U32_MIN && a <= U32_MAX;
> > + return a <= U32_MAX;
> > }
>
> I cannot find the related link. But IIRC, Alexei commented that
> the code is written this way to express the intention (within
> 32bit bounds) so this patch is unnecessary...
>

Yeah, I agree with Yonghong. I was about to reply.

Jingxiang, you are absolutely correct that a <= U32_MAX is redundant,
but I feel having both sides checked explicitly makes code more
readable.

> >
> > static void __reg_combine_64_into_32(struct bpf_reg_state *reg)

\
 
 \ /
  Last update: 2022-07-29 19:17    [W:0.467 / U:0.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site