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Mon, 28 Sep 2026 11:53:46 -0700 (PDT) Received: from localhost ([2a03:2880:ff:4e::]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-6d88221983fsm6277579eaf.3.2026.09.28.11.53.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 11:53:45 -0700 (PDT) From: Amery Hung To: bpf@vger.kernel.org Cc: alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, memxor@gmail.com, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v3 07/11] bpf: Check subprog arena arguments in the common path Date: Mon, 28 Sep 2026 11:53:30 -0700 Message-ID: <20260928185334.1004200-8-ameryhung@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260928185334.1004200-1-ameryhung@gmail.com> References: <20260928185334.1004200-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ARG_PTR_TO_ARENA accepts both arena pointers and scalars. The existing BPF-subprogram contract includes a constant-zero scalar; it is an arena address value rather than a conventional pointer rejected by nullability checking. Kfunc prototype generation already records this zero acceptance with PTR_MAYBE_NULL for both arena suffixes; separate JIT metadata determines whether the kernel callee receives the arena base or NULL. Apply the same call-site representation to the temporary BPF-subprogram prototype, then extend the guarded check_func_arg() path to cover arena arguments. Signed-off-by: Amery Hung --- kernel/bpf/verifier.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 659820a4b805..efb20e50c974 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10816,6 +10816,8 @@ static void gen_subprog_arg_proto(const struct bpf_subprog_info *sub, const stru * to protect against invalid memory access. */ arg_type = ARG_IGNORE; + } else if (base_type(arg_type) == ARG_PTR_TO_ARENA) { + arg_type |= PTR_MAYBE_NULL; } proto->arg_type[arg] = arg_type; t = btf_type_skip_modifiers(btf, args[arg].type, NULL); @@ -10881,7 +10883,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, nslots = btf_arg_slots(t); if (arg_type == ARG_SCALAR || arg_type == ARG_IGNORE || - arg_type == ARG_PTR_TO_CTX) { + arg_type == ARG_PTR_TO_CTX || + base_type(arg_type) == ARG_PTR_TO_ARENA) { ret = check_func_arg(env, arg, slot, 0, &meta, env->insn_idx); if (ret) return ret; @@ -10909,19 +10912,6 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog, reg_arg_name(env, argno)); return -EINVAL; } - } else if (base_type(arg_type) == ARG_PTR_TO_ARENA) { - /* - * Can pass any value and the kernel won't crash, but - * only PTR_TO_ARENA or SCALAR make sense. Everything - * else is a bug in the bpf program. Point it out to - * the user at the verification time instead of - * run-time debug nightmare. - */ - if (reg->type != PTR_TO_ARENA && reg->type != SCALAR_VALUE) { - bpf_log(log, "%s is not a pointer to arena or scalar.\n", - reg_arg_name(env, argno)); - return -EINVAL; - } } else if (arg_type == ARG_PTR_TO_DYNPTR) { ret = check_func_arg_reg_off(env, reg, argno, ARG_PTR_TO_DYNPTR); if (ret) -- 2.52.0