Re: [PATCH net] bonding: fix devconf_all NULL dereference when IPv6 is disabled

[Hangbin Liu]

On Tue, Jul 7, 2026 at 9:07 AM <zhangzl2013@xxxxxxx> wrote:
>
> From: Zhaolong Zhang <zhangzl68@xxxxxxxxxxxxxxx>
>
> When booting with the 'ipv6.disable=1' parameter, the devconf_all is
> never initialized because inet6_init() exits before addrconf_init() is
> called which initializes it. bond_send_validate(), however, will still
> call bond_ns_send_all() even ipv6 is indeed disabled. It will lead to
> NULL derefence of net->ipv6.devconf_all in ip6_pol_route().
>
>  BUG: kernel NULL pointer dereference, address: 000000000000000c
>  [...]
>  Workqueue: bond0 bond_arp_monitor [bonding]
>  RIP: 0010:ip6_pol_route+0x69/0x480
>  [...]
>  Call Trace:
>   <TASK>
>   ? srso_return_thunk+0x5/0x5f
>   ? __pfx_ip6_pol_route_output+0x10/0x10
>   fib6_rule_lookup+0xfe/0x260
>   ? wakeup_preempt+0x8a/0x90
>   ? srso_return_thunk+0x5/0x5f
>   ? srso_return_thunk+0x5/0x5f
>   ? sched_balance_rq+0x369/0x810
>   ip6_route_output_flags+0xd7/0x170
>   bond_ns_send_all+0xde/0x280 [bonding]
>   bond_ab_arp_probe+0x296/0x320 [bonding]
>   ? srso_return_thunk+0x5/0x5f
>   bond_activebackup_arp_mon+0xb4/0x2c0 [bonding]
>   process_one_work+0x196/0x370
>   worker_thread+0x1af/0x320
>   ? srso_return_thunk+0x5/0x5f
>   ? __pfx_worker_thread+0x10/0x10
>   kthread+0xe3/0x120
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork+0x199/0x260
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork_asm+0x1a/0x30
>   </TASK>
>
> Fix this by adding ipv6_mod_enabled() condition check in the caller.
>
> Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
> Signed-off-by: Qianheng Peng <pengqh1@xxxxxxxxxxxxxxx>
> Signed-off-by: Zhaolong Zhang <zhangzl68@xxxxxxxxxxxxxxx>
> ---
>  drivers/net/bonding/bond_main.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index e044fc733b8c..522eab060f9e 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -3455,7 +3455,8 @@ static void bond_send_validate(struct bonding *bond, struct slave *slave)
>  {
>         bond_arp_send_all(bond, slave);
>  #if IS_ENABLED(CONFIG_IPV6)
> -       bond_ns_send_all(bond, slave);
> +       if (likely(ipv6_mod_enabled()))
> +               bond_ns_send_all(bond, slave);
>  #endif
>  }
>

Thanks for your fix. Next time please use PATCHv2 with a change log.

Reviewed-by: Hangbin Liu <liuhangbin@xxxxxxxxx>