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([2001:41d0:303:db6b::]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-447b3d48517sm6183750f8f.5.2026.04.29.10.56.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2026 10:56:13 -0700 (PDT) From: Tristan Madani To: Pablo Neira Ayuso Cc: Florian Westphal , Phil Sutter , netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, Tristan Madani Subject: [PATCH 0/2] netfilter: fix NULL ops race in iptable lazy init Date: Wed, 29 Apr 2026 17:56:10 +0000 Message-ID: <20260429175613.1459342-1-tristmd@gmail.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Tristan Madani ipt_register_table() and ip6t_register_table() call xt_register_table() which adds the new table to the per-netns list, making it visible to other code paths. Only afterwards do they allocate the per-net copy of hook ops via kmemdup_array(). This leaves a window where the table is findable via xt_find_table() but has ops=NULL. If cleanup_net runs during this window (racing namespace teardown against lazy table init), ipt_unregister_table_pre_exit() / ip6t_unregister_table_pre_exit() finds the table and passes the NULL ops pointer to nf_unregister_net_hooks(), causing a general protection fault. Fix both ip_tables.c and ip6_tables.c by moving the ops allocation before xt_register_table(), so the table is never in the list with a NULL ops pointer. Tristan Madani (2): netfilter: ip_tables: allocate hook ops before making table visible netfilter: ip6_tables: allocate hook ops before making table visible net/ipv4/netfilter/ip_tables.c | 31 ++++++++++++++++--------------- net/ipv6/netfilter/ip6_tables.c | 28 ++++++++++++++++------------ 2 files changed, 32 insertions(+), 27 deletions(-) -- 2.47.3