netdev - Re: [PATCH 1/1] ipv6: Check AF_UNSPEC in ip6_route_multipath

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Message-ID: <u3HUdiCPiMCv5kkEVMXU9bKhZLDParnZCqUybez-bALHM78ymOclmc2pzUXgAGu-Bdwi30aV_LJkhicY2rwhZdjBzvYWyErXQpDQN3w4Ihs=@proton.me>
Date: Fri, 05 Sep 2025 22:12:04 +0000
From: Maksimilijan Marošević <maksimilijan.marosevic@...ton.me>
To: "kuba@...nel.org" <kuba@...nel.org>
Cc: "davem@...emloft.net" <davem@...emloft.net>, "dsahern@...nel.org" <dsahern@...nel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "syzbot+a259a17220263c2d73fc@...kaller.appspotmail.com" <syzbot+a259a17220263c2d73fc@...kaller.appspotmail.com>
Subject: Re: [PATCH 1/1] ipv6: Check AF_UNSPEC in ip6_route_multipath_add()

Hi Jakub,

Sorry for the delay. 
I've managed to devise a test-case that reliably reproduces the error, but I now believe the fix can be implemented better. Unfortunately, I haven't had the chance to work on the new fix these past couple of weeks.

I'll try to finish it this weekend and then run it through syzbot once more.

Maksimilijan

-------- Original Message --------
On 04/09/2025 18:03, Jakub Kicinski <kuba@...nel.org> wrote:

>  On Mon, 04 Aug 2025 20:42:53 +0000 Maksimilijan Marosevic wrote:
>  > This check was removed in commit e6f497955fb6 ("ipv6: Check GATEWAY
>  > in rtm_to_fib6_multipath_config().") as part of rt6_qualify_for ecmp().
>  > The author correctly recognises that rt6_qualify_for_ecmp() returns
>  > false if fb_nh_gw_family is set to AF_UNSPEC, but then mistakes
>  > AF_UNSPEC for AF_INET6 when reasoning that the check is unnecessary.
>  > This means certain malformed entries don't get caught in
>  > ip6_route_multipath_add().
>  >
>  > This patch reintroduces the AF_UNSPEC check while respecting changes
>  > of the initial patch.
>  
>  Hi Maksimilijan!
>  
>  Are you planning to repost this with a test?
>  If not I suppose we can enlist the author of the commit to help with
>  the selftest..
>