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Mon, 27 Jul 2026 16:15:55 -0700 (PDT) Message-ID: Subject: Re: [PATCH bpf-next v2 12/18] bpf: Handle NULL kfunc pointer args without a KF_ARG_PTR_TO_NULL type From: Eduard Zingerman To: Amery Hung , bpf@vger.kernel.org Cc: alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, memxor@gmail.com, kernel-team@meta.com Date: Mon, 27 Jul 2026 16:15:52 -0700 In-Reply-To: <20260724190813.1458271-13-ameryhung@gmail.com> References: <20260724190813.1458271-1-ameryhung@gmail.com> <20260724190813.1458271-13-ameryhung@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-10 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-07-24 at 12:08 -0700, Amery Hung wrote: > get_kfunc_ptr_arg_type() returned KF_ARG_PTR_TO_NULL when a nullable > pointer argument was passed a NULL register. This folded a register-state > decision (bpf_register_is_null()) into what is otherwise BTF-based > argument classification, and it short-circuited before the BTF_ID/MEM > resolution. >=20 > Drop KF_ARG_PTR_TO_NULL and handle the NULL case in check_kfunc_args() > instead: a nullable argument that is actually NULL is skipped. Note that > it is okay to skip even when it is a mem+size pair because the size > argument check has been moved to the scalar section. The skip is done > before get_kfunc_ptr_arg_type() so that a NULL passed to a nullable > non-scalar-struct argument is not newly rejected by the BTF_ID/MEM > resolution. >=20 > No functional change. >=20 > Signed-off-by: Amery Hung > --- Reviewed-by: Eduard Zingerman ...