Re: [PATCH 1/2 net v3] net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled
Fernando Fernandez Mancera <[email protected]>
| Newsgroups | gmane.linux.network.bridge,gmane.linux.network |
|---|---|
| Message-ID | <[email protected]> |
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 <[email protected]>
>> Closes: https://lore.kernel.org/netdev/CAHXs0ORzd62QOG-Fttqa2Cx_A_VFp=utE2H2VTX5nqfgs7LDxQ@mail.gmail.com/
>> Signed-off-by: Fernando Fernandez Mancera <[email protected]>
>
> Reviewed-by: Ido Schimmel <[email protected]>
>
> I assume you will remove ipv6_stub from the bridge in net-next
Yes, a patch series dropping ipv6_stub is cooking.