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Thu, 12 Nov 2026 12:46:38 -0800 (PST) Received: from localhost ([153.61.198.241]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b197d257a0sm6330400a91.11.2026.11.12.12.46.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Nov 2026 12:46:38 -0800 (PST) Content-Type: text/plain; charset=UTF-8 Date: Thu, 12 Nov 2026 20:46:37 +0000 Message-Id: Cc: , , , Subject: Re: [PATCH bpf v4] bpf: check cpu_possible() in per-cpu helpers and map callbacks From: "Alexei Starovoitov" To: "bo cao" , In-Reply-To: References: Content-Transfer-Encoding: 8bit X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Sun, Nov 08, 2026 at 06:43 PM bo cao wrote: > @@ -133,6 +133,10 @@ const struct bpf_func_proto bpf_map_peek_elem_proto = { > BPF_CALL_3(bpf_map_lookup_percpu_elem, struct bpf_map *, map, void *, key, u32, cpu) > { > WARN_ON_ONCE(!bpf_rcu_lock_held()); > + > + if (cpu >= nr_cpu_ids || !cpu_possible(cpu)) > + return 0; > + > return (unsigned long) map->ops->map_lookup_percpu_elem(map, key, cpu); bpf-ci is right. All three callbacks have the check. Drop this hunk. It's dead code. > if (returns_cpu_specific_alloc_ptr) { > - regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_ALLOC | MEM_RCU; > + regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_ALLOC | MEM_RCU | > + (ret_flag & PTR_MAYBE_NULL); This is a fix for a different bug. It doesn't need a sparse mask. bpf_per_cpu_ptr(p, -1) returns NULL on every machine. It may break existing progs and needs a separate discussion. pw-bot: cr