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Thu, 05 Nov 2026 08:39:30 -0800 (PST) Received: from localhost ([153.61.198.243]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b0b323cd47sm4574863a91.6.2026.11.05.08.39.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2026 08:39:29 -0800 (PST) Content-Type: text/plain; charset=UTF-8 Date: Thu, 05 Nov 2026 16:39:29 +0000 Message-Id: Cc: , Subject: Re: [PATCH] bpf: Add network namespace boundary inspection kfuncs From: "Alexei Starovoitov" To: "Abhishek Khade" , , , In-Reply-To: <20261105121642.38019-1-abhishekkhade69@gmail.com> References: <20261105121642.38019-1-abhishekkhade69@gmail.com> Content-Transfer-Encoding: 8bit X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Thu, Nov 05, 2026 at 04:16 AM Abhishek Khade wrote: > Currently, dereferencing task->nsproxy->net_ns directly via BPF CO-RE > presents safety and architectural challenges: No. The prog does all of it today without new kfuncs: inum = task->nsproxy->net_ns->ns.inum; is_init_net = inum == NET_NS_INIT_INO; The verifier accepts these loads in tp_btf, fentry and lsm progs. A load that faults reads zero. It doesn't crash. NET_NS_INIT_INO is uapi. No need for the address of init_net. For a socket it's sk->__sk_common.skc_net.net->ns.inum. Networking progs also have bpf_get_netns_cookie(). > + rcu_read_lock(); > + nsproxy = rcu_dereference(task->nsproxy); > + if (nsproxy) { > + net = READ_ONCE(nsproxy->net_ns); > + if (net) > + inum = net->ns.inum; This is a use-after-free when task != current. So much for 'this is safer than CO-RE' :( pw-bot: cr