netdev - Re: [PATCH net 1/2] geneve: should not call rt6

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Date:   Wed, 6 Feb 2019 20:04:17 +0100
From:   Stefano Brivio <sbrivio@...hat.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Hangbin Liu <liuhangbin@...il.com>, netdev@...r.kernel.org,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH net 1/2] geneve: should not call rt6_lookup() when ipv6
 was disabled

On Wed, 6 Feb 2019 10:54:01 -0800
David Ahern <dsahern@...il.com> wrote:

> On 2/6/19 4:51 AM, Hangbin Liu wrote:
> > When we add a new GENEVE device with IPv6 remote, checking only for
> > IS_ENABLED(CONFIG_IPV6) is not enough as we may disable IPv6 in kernel
> > cmd(ipv6.disable=1), which will cause a NULL pointer dereference.
> > 
> > Reported-by: Jianlin Shi <jishi@...hat.com>
> > Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> > ---
> >  drivers/net/geneve.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
> > index 58bbba8582b0..0658715581e3 100644
> > --- a/drivers/net/geneve.c
> > +++ b/drivers/net/geneve.c
> > @@ -1512,6 +1512,10 @@ static void geneve_link_config(struct net_device *dev,
> >  	}
> >  #if IS_ENABLED(CONFIG_IPV6)
> >  	case AF_INET6: {
> > +		struct inet6_dev *idev = in6_dev_get(dev);
> > +		if (!idev)
> > +			break;  
> 
> Since you don't need an idev reference rcu_access_pointer should be
> enough to say v6 is enabled on this device. ie., add a helper to check
> that rcu_access_pointer(dev->ip6_ptr) is non-NULL

I guess if (__in6_dev_get(dev)) is already good, no? This is called
under RTNL.

-- 
Stefano