From: Ido Schimmel <idosch@nvidia.com>
To: Fernando Fernandez Mancera <fmancera@suse.de>
Cc: netdev@vger.kernel.org, bridge@lists.linux.dev,
roopa@cumulusnetworks.com, sdf@fomichev.me, petrm@nvidia.com,
horms@kernel.org, razor@blackwall.org, pabeni@redhat.com,
kuba@kernel.org, edumazet@google.com, davem@davemloft.net,
andrew+netdev@lunn.ch, Guruprasad C P <gurucp2005@gmail.com>
Subject: Re: [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
Date: Thu, 5 Mar 2026 13:39:40 +0200 [thread overview]
Message-ID: <20260305113940.GA1359245@shredder> (raw)
In-Reply-To: <20260304120357.9778-1-fmancera@suse.de>
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
next prev parent reply other threads:[~2026-03-05 11:39 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
2026-03-05 11:41 ` [PATCH 1/2 net v3] net: bridge: " Fernando Fernandez Mancera
2026-03-05 13:29 ` Nikolay Aleksandrov
2026-03-05 16:10 ` patchwork-bot+netdevbpf
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