linux-kernel - Re: [PATCH] xfrm: Use correct address family in xfrm_state

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Message-ID: <20200928050727.GE20687@gauss3.secunet.de>
Date:   Mon, 28 Sep 2020 07:07:27 +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>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] xfrm: Use correct address family in xfrm_state_find

On Fri, Sep 25, 2020 at 02:42:56PM +1000, Herbert Xu wrote:
> Resend with proper subject.
>  
> ---8<---
> The struct flowi must never be interpreted by itself as its size
> depends on the address family.  Therefore it must always be grouped
> with its original family value.
> 
> In this particular instance, the original family value is lost in
> the function xfrm_state_find.  Therefore we get a bogus read when
> it's coupled with the wrong family which would occur with inter-
> family xfrm states.
> 
> This patch fixes it by keeping the original family value.
> 
> Note that the same bug could potentially occur in LSM through
> the xfrm_state_pol_flow_match hook.  I checked the current code
> there and it seems to be safe for now as only secid is used which
> is part of struct flowi_common.  But that API should be changed
> so that so that we don't get new bugs in the future.  We could
> do that by replacing fl with just secid or adding a family field.
> 
> Reported-by: syzbot+577fbac3145a6eb2e7a5@...kaller.appspotmail.com
> Fixes: 48b8d78315bf ("[XFRM]: State selection update to use inner...")
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

Applied, thanks a lot Herbert!