netdev - Re: [PATCH net] net: ipv6: prevent use after free in ip6_route_mpath

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Date:   Sun, 3 Jun 2018 08:40:37 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net] net: ipv6: prevent use after free in
 ip6_route_mpath_notify()

On 6/3/18 8:01 AM, David Ahern wrote:
> Is there a reproducer for the syzbot case?

One reproducer is to insert a route and then add a multipath route that
has a duplicate nexthop.e.g,:

ip -6 ro add vrf red 2001:db8:101::/64 nexthop via 2001:db8:1::2

ip -6 ro append vrf red 2001:db8:101::/64 nexthop via 2001:db8:1::4
nexthop via 2001:db8:1::2

Current net and next-next generates the trace; with the fix I proposed I
don't see it on either branch and I do see the expected notifications to
userspace.