Re: [PATCH net 3/6] ipv6: fix error handling in forwarding sysctl

[Nicolas Dichtel <nicolas.dichtel@6wind.com>]

Le 19/06/2026 à 12:28, Fernando Fernandez Mancera a écrit :
> On 6/19/26 11:34 AM, Nicolas Dichtel wrote:
>> Le 18/06/2026 à 18:22, Fernando Fernandez Mancera a écrit :
>>> When writing to the forwarding sysctl, if proc_dointvec() fails to parse
>>> the input, it returns a negative error code. The current implementation
>>> is overwriting that error for write operations.
>>>
>>> This results in a silent failure, it returns a successful write although
>>> the configuration was not modified at all. When modifying the "all"
>>> variant it can also modify the configuration of existing interfaces to
>>> the wrong value.
>>>
>>> Fix this by checking the return value of proc_dointvec() and returning
>>> early on failure.
>>>
>>> Fixes: b325fddb7f86 ("ipv6: Fix sysctl unregistration deadlock")
>> The bug existed before the git era.
>> Maybe
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>>
>>
> 
> 
> Hm, not really, AFAICS b325fddb7f86 is the first commit overwriting the return
> value from proc_dointvec(). See:
> 
> @@ -3983,7 +3986,7 @@ int addrconf_sysctl_forward(ctl_table *ctl, int write,
> struct file * filp,
>      ret = proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
> 
>      if (write)
> -        addrconf_fixup_forwarding(ctl, valp, val);
> +        ret = addrconf_fixup_forwarding(ctl, valp, val);
>      return ret;
>  }
Hmm, you're right.

Reviewed-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>