On Wed, Nov 29, 2023 at 10:33 PM Shung-Hsi Yu <shung-hsi.yu@xxxxxxxx> wrote:
>
> On Wed, Nov 29, 2023 at 04:04:03PM -0800, Andrii Nakryiko wrote:
> > Given we enforce a valid range for program and async callback return
> > value, we must mark R0 as precise to avoid incorrect state pruning.
>
> Looking at previous discussion[1], this commit fixes the potential
> "out-of-range r0 got state pruned" issue. To my best knowledge that
> means this commit would be needed all the way back in
>
> Fixes: b5dc0163d8fd ("bpf: precise scalar_value tracking")
>
> Is this wildly off?
No, I think you are right. Added Fixes: tag as suggested.
>
> 1: https://lore.kernel.org/r/20231031050324.1107444-4-andrii@xxxxxxxxxx
>
> > Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > ---
> > kernel/bpf/verifier.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index c54944af1bcc..2cd150d6d141 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -15138,6 +15138,10 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
> > return -EINVAL;
> > }
> >
> > + err = mark_chain_precision(env, regno);
> > + if (err)
> > + return err;
> > +
> > if (!retval_range_within(range, reg)) {
> > verbose_invalid_scalar(env, reg, range, exit_ctx, reg_name);
> > if (!is_subprog &&
