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([2620:10d:c090:500::2:8dac]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-13d13014d27sm18568791c88.4.2026.07.23.10.57.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jul 2026 10:57:59 -0700 (PDT) Message-ID: <22df73ce6c09065672d3a9406ae59c2cb264f96c.camel@gmail.com> Subject: Re: [PATCH bpf-next v3 1/3] bpf: Preserve pointer state for commuted arithmetic From: Eduard Zingerman To: Shung-Hsi Yu , Yiyang Chen Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Kumar Kartikeya Dwivedi , John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Shuah Khan , Emil Tsalapatis , Ihor Solodrai , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 23 Jul 2026 10:57:56 -0700 In-Reply-To: References: <004a83de52a36e9f3acd6c3fa2d0dfd0a013460d.1784696372.git.chenyy23@mails.tsinghua.edu.cn> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.1 (3.60.1-1.fc44) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2026-07-23 at 10:35 -0700, Eduard Zingerman wrote: > On Thu, 2026-07-23 at 12:25 +0800, Shung-Hsi Yu wrote: >=20 > ... >=20 > > The sole purpose of having orig_off_reg seem to be for satisfying the > > 'off_reg =3D=3D dst_reg' conditional in sanitize_err(). If that's the c= ase, > > maybe it is better to change sanitize_err to accept an ptr_is_dst_reg > > argument too. > >=20 > > And given now that we are starting to make more use of scratch register > > states, it seems better to get rid the likes of 'off_reg =3D=3D dst_reg= ' all > > together, and simply have ptr_is_dst_reg passed down by > > adjust_scalar_min_max_vals(). > >=20 > >=20 > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index 52be0a118cce..72d49f2a57a3 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -13505,13 +13505,13 @@ static int sanitize_ptr_alu(struct bpf_verifi= er_env *env, > > const struct bpf_reg_state *off_reg, > > struct bpf_reg_state *dst_reg, > > struct bpf_sanitize_info *info, > > - const bool commit_window) > > + const bool commit_window, > > + const bool ptr_is_dst_reg) >=20 > That's a bit invasive. I think the simplest thing to do is to drop > off_reg and dst_reg parameters from sanitize_err() and re-derive the > information about which one is a pointer. Scratch that, dst type is gone when sanitize_err() called.