From: Nikolay Aleksandrov <razor@blackwall.org>
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, idosch@nvidia.com, 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 15:29:41 +0200 [thread overview]
Message-ID: <aamFRR3rfa1TlHEF@penguin> (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>
> ---
> 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>
next prev parent reply other threads:[~2026-03-05 13:29 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 ` [PATCH 1/2 net v3] net: bridge: " Ido Schimmel
2026-03-05 11:41 ` Fernando Fernandez Mancera
2026-03-05 13:29 ` Nikolay Aleksandrov [this message]
2026-03-05 16:10 ` patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aamFRR3rfa1TlHEF@penguin \
--to=razor@blackwall.org \
--cc=andrew+netdev@lunn.ch \
--cc=bridge@lists.linux.dev \
--cc=davem@davemloft.net \
--cc=edumazet@google.com \
--cc=fmancera@suse.de \
--cc=gurucp2005@gmail.com \
--cc=horms@kernel.org \
--cc=idosch@nvidia.com \
--cc=kuba@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
--cc=petrm@nvidia.com \
--cc=roopa@cumulusnetworks.com \
--cc=sdf@fomichev.me \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.