linux-kernel - Re: kernel BUG at net/key/af

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Message-ID: <20171109113857.GA15280@gondor.apana.org.au>
Date:   Thu, 9 Nov 2017 22:38:57 +1100
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot 
        <bot+413384116f7f7dab7903d54c53fc4af6a4441965@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        syzkaller-bugs@...glegroups.com
Subject: Re: kernel BUG at net/key/af_key.c:LINE!

On Wed, Nov 08, 2017 at 08:59:15AM +0100, Dmitry Vyukov wrote:
>
> Also the repro needs to be compiled with -m32 (but it does not compile
> without it due to missing __NR_mmap2, so I guess you passed -m32).

OK that's what I was missing.  I had hacked it to compile in
64-bit :)

However, I still don't understand why it's crashing yet.  What is
clear is that we're getting a socket policy with xp->family set
to zero, and the policy is created via the xfrm code path (as
opposed to af_key).

The xfrm code path is meant to forbid the creation of such a policy.
I don't currently see how this is bypassing that check.  But
clearly it has found a way through the check since it's crashing.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt