From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Eduard Zingerman <eddyz87@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@linux.dev>,
Kernel Team <kernel-team@fb.com>,
Yonghong Song <yonghong.song@linux.dev>
Subject: Re: [PATCH bpf-next 2/3] bpf: use reg->var_off instead of reg->off for pointers
Date: Wed, 11 Feb 2026 18:23:38 -0800 [thread overview]
Message-ID: <CAADnVQLZh4Bk++vEW97mL0mMCUJu075vQFS2Kkhf9zXP5b2zLw@mail.gmail.com> (raw)
In-Reply-To: <20260211-ptrs-off-migration-v1-2-996c2a37b063@gmail.com>
On Wed, Feb 11, 2026 at 2:32 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> - In mark_ptr_or_null_reg() WARN_ON_ONCE() checks were removed
> because in some cases helpers that return local kptrs can now
> return pointers with non-zero '.var_off' (e.g., a pointer to
> a spin lock inside a map entry).
...
> @@ -17129,29 +17074,13 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
> {
> if (type_may_be_null(reg->type) && reg->id == id &&
> (is_rcu_reg(reg) || !WARN_ON_ONCE(!reg->id))) {
> - /* Old offset (both fixed and variable parts) should have been
> - * known-zero, because we don't allow pointer arithmetic on
> - * pointers that might be NULL. If we see this happening, don't
> - * convert the register.
> - *
> - * But in some cases, some helpers that return local kptrs
> - * advance offset for the returned pointer. In those cases, it
> - * is fine to expect to see reg->off.
> - */
> - if (WARN_ON_ONCE(reg->smin_value || reg->smax_value || !tnum_equals_const(reg->var_off, 0)))
> - return;
> - if (!(type_is_ptr_alloc_obj(reg->type) || type_is_non_owning_ref(reg->type)) &&
> - WARN_ON_ONCE(reg->off))
> - return;
> -
This part looks overly aggressive to me.
I don't remember seeing these warns, so any known code or syzbot
is not triggering it, but can we keep them?
The first warn can stay as-is, no?
And the 2nd can be converted to tnum_equals_const() too ?
next prev parent reply other threads:[~2026-02-12 2:23 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-11 22:31 [PATCH bpf-next 0/3] bpf: consolidate pointer offset tracking in var_off Eduard Zingerman
2026-02-11 22:31 ` [PATCH bpf-next 1/3] bpf: split check_reg_sane_offset() in two parts Eduard Zingerman
2026-02-11 22:31 ` [PATCH bpf-next 2/3] bpf: use reg->var_off instead of reg->off for pointers Eduard Zingerman
2026-02-12 2:23 ` Alexei Starovoitov [this message]
2026-02-12 5:06 ` Eduard Zingerman
2026-02-11 22:31 ` [PATCH bpf-next 3/3] bpf: rename bpf_reg_state->off to bpf_reg_state->delta Eduard Zingerman
2026-02-11 23:08 ` bot+bpf-ci
2026-02-11 23:14 ` Eduard Zingerman
2026-02-12 3:06 ` kernel test robot
2026-02-12 8:15 ` kernel test robot
2026-02-12 8:15 ` kernel test robot
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