[PATCH 5.10 050/491] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled

Greg Kroah-Hartman
2026-04-13T16:44:46Z

From: Fernando Fernandez Mancera <fmancera@suse.de>

[ Upstream commit e5e890630533bdc15b26a34bb8e7ef539bdf1322 ]

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:
<IRQ>
? 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 <gurucp2005@gmail.com>
Closes: https://lore.kernel.org/netdev/CAHXs0ORzd62QOG-Fttqa2Cx_A_VFp=utE2H2VTX5nqfgs7LDxQ@mail.gmail.com/
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20260304120357.9778-1-fmancera@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 84e37108c6b5e..2c59e3f918ca2 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -70,7 +70,7 @@ 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 f9d4b86e3186d..4d7e99a547784 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -124,7 +124,7 @@ 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) +
--
2.51.0