* [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
@ 2026-03-04 12:03 Fernando Fernandez Mancera
2026-03-04 12:03 ` [PATCH 2/2 net v3] net: vxlan: " Fernando Fernandez Mancera
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: Fernando Fernandez Mancera @ 2026-03-04 12:03 UTC (permalink / raw)
To: netdev
Cc: bridge, roopa, sdf, petrm, horms, idosch, razor, pabeni, kuba,
edumazet, davem, andrew+netdev, Fernando Fernandez Mancera,
Guruprasad C P
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>
---
v2: use ipv6_mod_enabled() instead of a null check and replace the check
on the caller
v3: no changes
---
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
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 2/2 net v3] net: vxlan: fix nd_tbl NULL dereference when IPv6 is disabled
2026-03-04 12:03 [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled Fernando Fernandez Mancera
@ 2026-03-04 12:03 ` Fernando Fernandez Mancera
2026-03-05 11:39 ` [PATCH 1/2 net v3] net: bridge: " Ido Schimmel
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Fernando Fernandez Mancera @ 2026-03-04 12:03 UTC (permalink / raw)
To: netdev
Cc: bridge, roopa, sdf, petrm, horms, idosch, razor, pabeni, kuba,
edumazet, davem, andrew+netdev, Fernando Fernandez Mancera
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. If an IPv6 packet is injected into the interface,
route_shortcircuit() is called and a NULL pointer dereference happens on
neigh_lookup().
BUG: kernel NULL pointer dereference, address: 0000000000000380
Oops: Oops: 0000 [#1] SMP NOPTI
[...]
RIP: 0010:neigh_lookup+0x20/0x270
[...]
Call Trace:
<TASK>
vxlan_xmit+0x638/0x1ef0 [vxlan]
dev_hard_start_xmit+0x9e/0x2e0
__dev_queue_xmit+0xbee/0x14e0
packet_sendmsg+0x116f/0x1930
__sys_sendto+0x1f5/0x200
__x64_sys_sendto+0x24/0x30
do_syscall_64+0x12f/0x1590
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Fix this by adding an early check on route_shortcircuit() when protocol
is ETH_P_IPV6. Note that ipv6_mod_enabled() cannot be used here because
VXLAN can be built-in even when IPv6 is built as a module.
Fixes: e15a00aafa4b ("vxlan: add ipv6 route short circuit support")
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
v2: use ipv6_mod_enabled() instead of a NULL check
v3: go back to nd_tbl NULL check as ipv6_mod_enabled() might not be
available. Added a comment so it doesn't seem random.
---
drivers/net/vxlan/vxlan_core.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 05558b6afecd..17c941aac32d 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -2130,6 +2130,11 @@ static bool route_shortcircuit(struct net_device *dev, struct sk_buff *skb)
{
struct ipv6hdr *pip6;
+ /* check if nd_tbl is not initiliazed due to
+ * ipv6.disable=1 set during boot
+ */
+ if (!ipv6_stub->nd_tbl)
+ return false;
if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
return false;
pip6 = ipv6_hdr(skb);
--
2.53.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
2026-03-04 12:03 [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled Fernando Fernandez Mancera
2026-03-04 12:03 ` [PATCH 2/2 net v3] net: vxlan: " Fernando Fernandez Mancera
@ 2026-03-05 11:39 ` Ido Schimmel
2026-03-05 11:41 ` Fernando Fernandez Mancera
2026-03-05 13:29 ` Nikolay Aleksandrov
2026-03-05 16:10 ` patchwork-bot+netdevbpf
3 siblings, 1 reply; 6+ messages in thread
From: Ido Schimmel @ 2026-03-05 11:39 UTC (permalink / raw)
To: Fernando Fernandez Mancera
Cc: netdev, bridge, roopa, sdf, petrm, horms, razor, pabeni, kuba,
edumazet, davem, andrew+netdev, Guruprasad C P
On Wed, Mar 04, 2026 at 01:03:56PM +0100, Fernando Fernandez Mancera wrote:
> 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>
I assume you will remove ipv6_stub from the bridge in net-next
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
2026-03-05 11:39 ` [PATCH 1/2 net v3] net: bridge: " Ido Schimmel
@ 2026-03-05 11:41 ` Fernando Fernandez Mancera
0 siblings, 0 replies; 6+ messages in thread
From: Fernando Fernandez Mancera @ 2026-03-05 11:41 UTC (permalink / raw)
To: Ido Schimmel
Cc: netdev, bridge, roopa, sdf, petrm, horms, razor, pabeni, kuba,
edumazet, davem, andrew+netdev, Guruprasad C P
On 3/5/26 12:39 PM, Ido Schimmel wrote:
> On Wed, Mar 04, 2026 at 01:03:56PM +0100, Fernando Fernandez Mancera wrote:
>> 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>
>
> I assume you will remove ipv6_stub from the bridge in net-next
Yes, a patch series dropping ipv6_stub is cooking.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
2026-03-04 12:03 [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled Fernando Fernandez Mancera
2026-03-04 12:03 ` [PATCH 2/2 net v3] net: vxlan: " Fernando Fernandez Mancera
2026-03-05 11:39 ` [PATCH 1/2 net v3] net: bridge: " Ido Schimmel
@ 2026-03-05 13:29 ` Nikolay Aleksandrov
2026-03-05 16:10 ` patchwork-bot+netdevbpf
3 siblings, 0 replies; 6+ messages in thread
From: Nikolay Aleksandrov @ 2026-03-05 13:29 UTC (permalink / raw)
To: Fernando Fernandez Mancera
Cc: netdev, bridge, roopa, sdf, petrm, horms, idosch, pabeni, kuba,
edumazet, davem, andrew+netdev, Guruprasad C P
On Wed, Mar 04, 2026 at 01:03:56PM +0100, Fernando Fernandez Mancera wrote:
> 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>
> ---
> v2: use ipv6_mod_enabled() instead of a null check and replace the check
> on the caller
> v3: no changes
> ---
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
2026-03-04 12:03 [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled Fernando Fernandez Mancera
` (2 preceding siblings ...)
2026-03-05 13:29 ` Nikolay Aleksandrov
@ 2026-03-05 16:10 ` patchwork-bot+netdevbpf
3 siblings, 0 replies; 6+ messages in thread
From: patchwork-bot+netdevbpf @ 2026-03-05 16:10 UTC (permalink / raw)
To: Fernando Fernandez Mancera
Cc: netdev, bridge, roopa, sdf, petrm, horms, idosch, razor, pabeni,
kuba, edumazet, davem, andrew+netdev, gurucp2005
Hello:
This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:
On Wed, 4 Mar 2026 13:03:56 +0100 you wrote:
> 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.
>
> [...]
Here is the summary with links:
- [1/2,net,v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
https://git.kernel.org/netdev/net/c/e5e890630533
- [2/2,net,v3] net: vxlan: fix nd_tbl NULL dereference when IPv6 is disabled
https://git.kernel.org/netdev/net/c/168ff39e4758
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
^ permalink raw reply [flat|nested] 6+ messages in thread
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2026-03-04 12:03 [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled Fernando Fernandez Mancera
2026-03-04 12:03 ` [PATCH 2/2 net v3] net: vxlan: " Fernando Fernandez Mancera
2026-03-05 11:39 ` [PATCH 1/2 net v3] net: bridge: " Ido Schimmel
2026-03-05 11:41 ` Fernando Fernandez Mancera
2026-03-05 13:29 ` Nikolay Aleksandrov
2026-03-05 16:10 ` patchwork-bot+netdevbpf
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