linux-kernel - Re: netlink: NULL timer crash

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Message-ID: <1490297548.9687.0.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 23 Mar 2017 12:32:28 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     edumazet@...gle.com, dvyukov@...gle.com, xiyou.wangcong@...il.com,
        herbert@...dor.apana.org.au, ast@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller@...glegroups.com
Subject: Re: netlink: NULL timer crash

On Thu, 2017-03-23 at 12:00 -0700, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Thu, 23 Mar 2017 09:00:58 -0700
> 
> > On Thu, 2017-03-23 at 07:53 -0700, Eric Dumazet wrote:
> > 
> >> Nice !
> >> 
> >> Looks like neigh->ops->solicit is NULL
> > 
> > Apparently we allow admins to do really stupid things with neighbours
> > on tunnels.
> > 
> > Following patch should avoid the crash.
> > 
> > Anyone has better ideas ?
> 
> This is probably good enough for now, but you need to also handle
> dn_neigh_ops.
> 
> Another way to solve this is to add a NULL method check to the
> one spot where we invoke this method.  That clearly shows that
> the method is optional.

Yes, this would be a one liner. I will post this in a minute.

Thanks.