Re: [PATCH net v2 2/4] ipv6: fix source address selection with route leak

[David Ahern <dsahern@kernel.org>]

On 7/5/24 8:52 AM, Nicolas Dichtel wrote:
> diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
> index a18ed24fed94..a7c27f0c6bce 100644
> --- a/include/net/ip6_route.h
> +++ b/include/net/ip6_route.h
> @@ -127,18 +127,23 @@ void rt6_age_exceptions(struct fib6_info *f6i, struct fib6_gc_args *gc_args,
>  
>  static inline int ip6_route_get_saddr(struct net *net, struct fib6_info *f6i,
>  				      const struct in6_addr *daddr,
> -				      unsigned int prefs,
> +				      unsigned int prefs, int l3mdev_index,
>  				      struct in6_addr *saddr)
>  {
> +	struct net_device *l3mdev;
> +	struct net_device *dev;
> +	bool same_vrf;
>  	int err = 0;
>  
> -	if (f6i && f6i->fib6_prefsrc.plen) {
> +	rcu_read_lock();
> +	l3mdev = dev_get_by_index_rcu(net, l3mdev_index);
> +	dev = f6i ? fib6_info_nh_dev(f6i) : NULL;
> +	same_vrf = l3mdev == NULL || l3mdev_master_dev_rcu(dev) == l3mdev;

!l3mdev; checkpatch should complain

> +	if (f6i && f6i->fib6_prefsrc.plen && same_vrf)
>  		*saddr = f6i->fib6_prefsrc.addr;
> -	} else {
> -		struct net_device *dev = f6i ? fib6_info_nh_dev(f6i) : NULL;
> -
> -		err = ipv6_dev_get_saddr(net, dev, daddr, prefs, saddr);
> -	}
> +	else
> +		err = ipv6_dev_get_saddr(net, same_vrf ? dev : l3mdev, daddr, prefs, saddr);
> +	rcu_read_unlock();
>  
>  	return err;
>  }

lot of logic lines jammed together. put a new line after the read_lock()
and before the unlock().