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

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 07/07/2026 02:06, zhangzl2013@126.com wrote:
> From: Zhaolong Zhang <zhangzl68@chinatelecom.cn>
> 
> 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@chinatelecom.cn>
> Signed-off-by: Zhaolong Zhang <zhangzl68@chinatelecom.cn>
> ---
>   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
>   }
>   

ipv6_mod_enabled() doesn't depend on CONFIG_IPV6, please, remove
#if IS_ENABLED as well