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([2620:10d:c090:600::76f6]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2beab3a0c34sm15964777eec.7.2026.03.16.13.57.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Mar 2026 13:57:12 -0700 (PDT) Message-ID: <29e5aa5fc5a9724d0c3737297fbecd3a3eae76cd.camel@gmail.com> Subject: Re: [RFC PATCH bpf-next v2 01/11] bpf: Set kfunc dynptr arg type flag based on prototype From: Eduard Zingerman To: Amery Hung , bpf@vger.kernel.org Cc: netdev@vger.kernel.org, alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, memxor@gmail.com, martin.lau@kernel.org, kernel-team@meta.com Date: Mon, 16 Mar 2026 13:57:10 -0700 In-Reply-To: <20260307064439.3247440-2-ameryhung@gmail.com> References: <20260307064439.3247440-1-ameryhung@gmail.com> <20260307064439.3247440-2-ameryhung@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 (3.58.2-1.fc43) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-03-06 at 22:44 -0800, Amery Hung wrote: > The verifier should decide whether a dynptr argument is read-only > based on if the type is "const struct bpf_dynptr *", not the type of > the register passed to the kfunc. This currently does not cause issues > because existing kfuncs that mutate struct bpf_dynptr are constructors > (e.g., bpf_dynptr_from_xxx and bpf_dynptr_clone). These kfuncs have > additional check in process_dynptr_func() to make sure the stack slot > does not contain initialized dynptr. Nonetheless, this should still be > fixed to avoid future issues when there is a non-constructor dynptr > kfunc that can mutate dynptr. This is also a small step toward unifying > kfunc and helper handling in the verifier, where the first step is to > generate kfunc prototype similar to bpf_func_proto before the main > verification loop. >=20 > We also need to correctly mark some kfunc arguments as "const struct > bpf_dynptr *" to align with other kfuncs that take non-mutable dynptr > argument and to not break their usage. Adding const qualifier does > not break backward compatibility. >=20 > Signed-off-by: Amery Hung > --- Acked-by: Eduard Zingerman [...]