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([2001:41d0:303:db6b::]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-447b3d48517sm6183750f8f.5.2026.04.29.10.56.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2026 10:56:14 -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 1/2] netfilter: ip_tables: allocate hook ops before making table visible Date: Wed, 29 Apr 2026 17:56:11 +0000 Message-ID: <20260429175613.1459342-2-tristmd@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260429175613.1459342-1-tristmd@gmail.com> References: <20260429175613.1459342-1-tristmd@gmail.com> 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() adds the table to the per-netns list via xt_register_table() before allocating the per-netns hook ops copy via kmemdup_array(). This leaves a window where the table is visible in the list with ops=NULL. If cleanup_net() runs during this window (e.g. due to concurrent netns teardown with failslab-induced allocation failures), the pre_exit callback finds the table via xt_find_table() and passes the NULL ops pointer to nf_unregister_net_hooks(), causing a NULL pointer dereference: general protection fault in nf_unregister_net_hooks+0xbc/0x150 RIP: nf_unregister_net_hooks (net/netfilter/core.c:613) Call Trace: ipt_unregister_table_pre_exit iptable_mangle_net_pre_exit ops_pre_exit_list cleanup_net Fix by moving the ops allocation before xt_register_table() so the table is never in the list without valid ops. Fixes: ae689334225f ("netfilter: ip_tables: pass table pointer via nf_hook_ops") Cc: stable@vger.kernel.org Signed-off-by: Tristan Madani --- net/ipv4/netfilter/ip_tables.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 23c8deff8095a..c47bc776eb4f2 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -1745,6 +1745,21 @@ int ipt_register_table(struct net *net, const struct xt_table *table, return ret; } + if (template_ops) { + num_ops = hweight32(table->valid_hooks); + if (num_ops == 0) { + xt_free_table_info(newinfo); + return -EINVAL; + } + + ops = kmemdup_array(template_ops, num_ops, sizeof(*ops), + GFP_KERNEL); + if (!ops) { + xt_free_table_info(newinfo); + return -ENOMEM; + } + } + new_table = xt_register_table(net, table, &bootstrap, newinfo); if (IS_ERR(new_table)) { struct ipt_entry *iter; @@ -1752,27 +1767,13 @@ int ipt_register_table(struct net *net, const struct xt_table *table, xt_entry_foreach(iter, loc_cpu_entry, newinfo->size) cleanup_entry(iter, net); xt_free_table_info(newinfo); + kfree(ops); return PTR_ERR(new_table); } - /* No template? No need to do anything. This is used by 'nat' table, it registers - * with the nat core instead of the netfilter core. - */ if (!template_ops) return 0; - num_ops = hweight32(table->valid_hooks); - if (num_ops == 0) { - ret = -EINVAL; - goto out_free; - } - - ops = kmemdup_array(template_ops, num_ops, sizeof(*ops), GFP_KERNEL); - if (!ops) { - ret = -ENOMEM; - goto out_free; - } - for (i = 0; i < num_ops; i++) ops[i].priv = new_table; -- 2.47.3