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Mon, 2 Mar 2026 14:08:56 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id O56TDPiZpWnCJAAAD6G6ig (envelope-from ); Mon, 02 Mar 2026 14:08:56 +0000 From: Fernando Fernandez Mancera To: netdev@vger.kernel.org Cc: bridge@lists.linux.dev, roopa@cumulusnetworks.com, sdf@fomichev.me, petrm@nvidia.com, horms@kernel.org, idosch@nvidia.com, razor@blackwall.org, pabeni@redhat.com, kuba@kernel.org, edumazet@google.com, davem@davemloft.net, andrew+netdev@lunn.ch, Fernando Fernandez Mancera , Guruprasad C P Subject: [PATCH 1/2 net v2] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled Date: Mon, 2 Mar 2026 15:08:46 +0100 Message-ID: <20260302140847.5941-1-fmancera@suse.de> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-1.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; 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TAGGED_RCPT(0.00)[netdev]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -1.51 X-Spam-Level: X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Queue-Id: 1E3395BD5C When booting with the 'ipv6.disable=1' parameter, the nd_tbl is never initialized because inet6_init() exits before ndisc_init() is called which initializes it. Then, if neigh_suppress is enabled and an ICMPv6 Neighbor Discovery packet reaches the bridge, br_do_suppress_nd() will dereference ipv6_stub->nd_tbl which is NULL, passing it to neigh_lookup(). This causes a kernel NULL pointer dereference. BUG: kernel NULL pointer dereference, address: 0000000000000268 Oops: 0000 [#1] PREEMPT SMP NOPTI [...] RIP: 0010:neigh_lookup+0x16/0xe0 [...] Call Trace: ? neigh_lookup+0x16/0xe0 br_do_suppress_nd+0x160/0x290 [bridge] br_handle_frame_finish+0x500/0x620 [bridge] br_handle_frame+0x353/0x440 [bridge] __netif_receive_skb_core.constprop.0+0x298/0x1110 __netif_receive_skb_one_core+0x3d/0xa0 process_backlog+0xa0/0x140 __napi_poll+0x2c/0x170 net_rx_action+0x2c4/0x3a0 handle_softirqs+0xd0/0x270 do_softirq+0x3f/0x60 Fix this by replacing IS_ENABLED(IPV6) call with ipv6_mod_enabled() in the callers. This is in essence disabling NS/NA suppression when IPv6 is disabled. Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports") Reported-by: Guruprasad C P Closes: https://lore.kernel.org/netdev/CAHXs0ORzd62QOG-Fttqa2Cx_A_VFp=utE2H2VTX5nqfgs7LDxQ@mail.gmail.com/ Signed-off-by: Fernando Fernandez Mancera --- v2: use ipv6_mod_enabled() instead of a null check and replace the check on the caller --- net/bridge/br_device.c | 2 +- net/bridge/br_input.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index ee01122f466f..f7502e62dd35 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -74,7 +74,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev) eth_hdr(skb)->h_proto == htons(ETH_P_RARP)) && br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED)) { br_do_proxy_suppress_arp(skb, br, vid, NULL); - } else if (IS_ENABLED(CONFIG_IPV6) && + } else if (ipv6_mod_enabled() && skb->protocol == htons(ETH_P_IPV6) && br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED) && pskb_may_pull(skb, sizeof(struct ipv6hdr) + diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c index 1405f1061a54..2cbae0f9ae1f 100644 --- a/net/bridge/br_input.c +++ b/net/bridge/br_input.c @@ -170,7 +170,7 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb (skb->protocol == htons(ETH_P_ARP) || skb->protocol == htons(ETH_P_RARP))) { br_do_proxy_suppress_arp(skb, br, vid, p); - } else if (IS_ENABLED(CONFIG_IPV6) && + } else if (ipv6_mod_enabled() && skb->protocol == htons(ETH_P_IPV6) && br_opt_get(br, BROPT_NEIGH_SUPPRESS_ENABLED) && pskb_may_pull(skb, sizeof(struct ipv6hdr) + -- 2.53.0