linux-kernel - Re: [PATCH] net: key: af_key: Fix possible null-pointer dereferences in pfkey_send_policy

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Date:   Sat, 27 Jul 2019 10:32:00 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Jeremy Sowden <jeremy@...zel.net>
CC:     Jia-Ju Bai <baijiaju1990@...il.com>, <herbert@...dor.apana.org.au>,
        <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: key: af_key: Fix possible null-pointer dereferences
 in pfkey_send_policy_notify()

On Fri, Jul 26, 2019 at 09:15:55PM +0100, Jeremy Sowden wrote:
> On 2019-07-26, at 11:45:14 +0200, Steffen Klassert wrote:
> > On Wed, Jul 24, 2019 at 05:35:09PM +0800, Jia-Ju Bai wrote:
> > >
> > > diff --git a/net/key/af_key.c b/net/key/af_key.c
> > > index b67ed3a8486c..ced54144d5fd 100644
> > > --- a/net/key/af_key.c
> > > +++ b/net/key/af_key.c
> > > @@ -3087,6 +3087,8 @@ static int pfkey_send_policy_notify(struct xfrm_policy *xp, int dir, const struc
> > >  	case XFRM_MSG_DELPOLICY:
> > >  	case XFRM_MSG_NEWPOLICY:
> > >  	case XFRM_MSG_UPDPOLICY:
> > > +		if (!xp)
> > > +			break;
> >
> > I think this can not happen. Who sends one of these notifications
> > without a pointer to the policy?
> 
> I had a quick grep and found two places where km_policy_notify is passed
> NULL as the policy:
> 
>   $ grep -rn '\<km_policy_notify(NULL,' net/
>   net/xfrm/xfrm_user.c:2154:      km_policy_notify(NULL, 0, &c);
>   net/key/af_key.c:2788:  km_policy_notify(NULL, 0, &c);
> 
> They occur in xfrm_flush_policy() and pfkey_spdflush() respectively.

Yes, but these two send a XFRM_MSG_FLUSHPOLICY notify.
This does not trigger the code that is changed here.