On 8/4/25 10:42 PM, 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.

Reported-by: syzbot+a259a17220263c2d73fc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=a259a17220263c2d73fc
Fixes: e6f497955fb6 ("ipv6: Check GATEWAY in rtm_to_fib6_multipath_config().")
Signed-off-by: Maksimilijan Marosevic <redacted>

Please resend in a 2 patches series including an additional self-test as
asked by David.

Also please insert into the subj prefix the target tree ('net' in this
case) and add Kuniyuki into the CC list.

Thanks,

Paolo