netdev - Re: KASAN: stack-out-of-bounds Read in xfrm_selector

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Message-ID: <20200924080205.GD20687@gauss3.secunet.de>
Date:   Thu, 24 Sep 2020 10:02:05 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
CC:     syzbot <syzbot+577fbac3145a6eb2e7a5@...kaller.appspotmail.com>,
        <davem@...emloft.net>, <kuba@...nel.org>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: stack-out-of-bounds Read in xfrm_selector_match (2)

On Thu, Sep 24, 2020 at 05:43:51PM +1000, Herbert Xu wrote:
> On Thu, Sep 24, 2020 at 09:40:26AM +0200, Steffen Klassert wrote:
> >
> > This is yet another ipv4 mapped ipv6 address with IPsec socket policy
> > combination bug, and I'm sure it is not the last one. We could fix this
> > one by adding another check to match the address family of the policy
> > and the SA selector, but maybe it is better to think about how this
> > should work at all.
> > 
> > We can have only one socket policy for each direction and that
> > policy accepts either ipv4 or ipv6. We treat this ipv4 mapped ipv6
> > address as ipv4 and pass it down the ipv4 stack, so this dual usage
> > will not work with a socket policy. Maybe we can require IPV6_V6ONLY
> > for sockets with policy attached. Thoughts?
> 
> I'm looking at the history of this and it used to work at the start
> because you'd always interpret the flow object with a family.  This
> appears to have been lost with 8444cf712c5f71845cba9dc30d8f530ff0d5ff83. 

I'm sure it can be fixed to work with either ipv4 or ipv6.
If I understand that right, it should be possible to talk
ipv4 and ipv6 through that socket, but the policy will
accept only one address family.

> I'm working on a fix.

Thanks!