Re: [PATCH net v2 1/4] ipv4: fix source address selection with route leak

[David Ahern <dsahern@kernel.org>]

On 7/5/24 8:52 AM, Nicolas Dichtel wrote:
> By default, an address assigned to the output interface is selected when
> the source address is not specified. This is problematic when a route,
> configured in a vrf, uses an interface from another vrf (aka route leak).
> The original vrf does not own the selected source address.
> 
> Let's add a check against the output interface and call the appropriate
> function to select the source address.
> 
> CC: stable@vger.kernel.org
> Fixes: 8cbb512c923d ("net: Add source address lookup op for VRF")
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> ---
>  net/ipv4/fib_semantics.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
> index f669da98d11d..459082f4936d 100644
> --- a/net/ipv4/fib_semantics.c
> +++ b/net/ipv4/fib_semantics.c
> @@ -2270,6 +2270,13 @@ void fib_select_path(struct net *net, struct fib_result *res,
>  		fib_select_default(fl4, res);
>  
>  check_saddr:
> -	if (!fl4->saddr)
> -		fl4->saddr = fib_result_prefsrc(net, res);
> +	if (!fl4->saddr) {
> +		struct net_device *l3mdev = dev_get_by_index_rcu(net, fl4->flowi4_l3mdev);

long line length. separate setting the value:

		struct net_device *l3mdev;

		l3mdev = dev_get_by_index_rcu(net, fl4->flowi4_l3mdev);

> +
> +		if (!l3mdev ||
> +		    l3mdev_master_dev_rcu(FIB_RES_DEV(*res)) == l3mdev)
> +			fl4->saddr = fib_result_prefsrc(net, res);
> +		else
> +			fl4->saddr = inet_select_addr(l3mdev, 0, RT_SCOPE_LINK);
> +	}
>  }