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([2620:10d:c090:500::2:8a9]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-302977a9474sm739335eec.25.2026.05.13.15.37.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 13 May 2026 15:37:28 -0700 (PDT) Message-ID: <0419643c9a04bf0824066742e52e3f197b43909b.camel@gmail.com> Subject: Re: [PATCH RESEND bpf-next v10 7/8] bpf: allow non-owning list-node args via __nonown_allowed From: Eduard Zingerman To: Kaitao cheng , ast@kernel.org, corbet@lwn.net, martin.lau@linux.dev, daniel@iogearbox.net, andrii@kernel.org, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, chengkaitao@kylinos.cn, skhan@linuxfoundation.org, memxor@gmail.com Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, vmalik@redhat.com, linux-kselftest@vger.kernel.org Date: Wed, 13 May 2026 15:37:25 -0700 In-Reply-To: <20260512055919.95716-8-kaitao.cheng@linux.dev> References: <20260512055919.95716-1-kaitao.cheng@linux.dev> <20260512055919.95716-8-kaitao.cheng@linux.dev> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-05-12 at 13:59 +0800, Kaitao cheng wrote: > From: Kaitao Cheng >=20 > KF_ARG_PTR_TO_LIST_NODE normally requires an owning reference > (PTR_TO_BTF_ID | MEM_ALLOC with ref_obj_id). Introduce and use > the __nonown_allowed annotation on selected list-node arguments > so non-owning references with ref_obj_id=3D=3D0 are accepted as well. >=20 > This enables passing bpf_list_front() / bpf_list_back() results to: >=20 > bpf_list_add() as insertion point (prev) > bpf_list_del() as deletion target (node) > bpf_list_is_first/last() as query target (node) >=20 > Verifier keeps existing owning-ref checks by default; only arguments > annotated with __nonown_allowed bypass MEM_ALLOC/ref_obj_id checks > and then follow the same list-node validation path. >=20 > Signed-off-by: Kaitao Cheng > --- Reviewed-by: Eduard Zingerman [...] > @@ -12017,6 +12022,13 @@ static int check_kfunc_args(struct bpf_verifier_= env *env, struct bpf_kfunc_call_ > return ret; > break; > case KF_ARG_PTR_TO_LIST_NODE: > + if (is_kfunc_arg_nonown_allowed(btf, &args[i]) && > + type_is_non_owning_ref(reg->type) && !reg->ref_obj_id) { ^^^^^^^^^^= ^^^^^^ Nit: I think this check is redundant, type_is_no= n_owning_ref() should suffice. > + /* Allow bpf_list_front/back return value for > + * __nonown_allowed list-node arguments. > + */ > + goto check_ok; > + } > if (reg->type !=3D (PTR_TO_BTF_ID | MEM_ALLOC)) { > verbose(env, "%s expected pointer to allocated object\n", > reg_arg_name(env, argno)); [...]