linux-kernel - Re: [PATCH v3 0/3] Send audit/procinfo/cgroup data in socket-level control message

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Date:	Wed, 04 Sep 2013 08:30:21 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jan Kaluza <jkaluza@...hat.com>, davem@...emloft.net,
	LKML <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
	eparis@...hat.com, tj@...nel.org, lizefan@...wei.com,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	viro@...iv.linux.org.uk
Subject: Re: [PATCH v3 0/3] Send audit/procinfo/cgroup data in socket-level
 control message

On Wed, 2013-09-04 at 11:20 -0400, Richard Guy Briggs wrote:
> On Wed, Sep 04, 2013 at 10:58:30AM -0400, Richard Guy Briggs wrote:
> > On Wed, Sep 04, 2013 at 12:42:26AM -0700, Eric W. Biederman wrote:
> > > Jan Kaluza <jkaluza@...hat.com> writes:
> > > > this patchset against net-next (applies also to linux-next) adds 3 new types
> > > > of "Socket"-level control message (SCM_AUDIT, SCM_PROCINFO and SCM_CGROUP).
> > 
> > > By my count you have overflowed cb in struct sk_buff and are stomping on
> > > _skb_refdest.
> > 
> > For patch1/3 I count 56/48, then for patch3 I get 48/48.  Jan, you might
> > do the conversion to a pointer in patch1/3 to avoid bisect breakage.
> 
> Wait, that __aligned(8) is for cb[48], not for the contents.
> 
> For patch1/3 I count 28/48 on 32-bit, 36/48 on 64-bit (or would that be
> 56 by default on 64-bit arches without aligned specified?), then for
> patch3 I get 24/48 on 32 and 40/48 on 64 (or again 48/48 by default?).

Do not count, just add this :

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 86de99a..5b61320 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1329,6 +1329,7 @@ static void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
 {
 	int i;
 
+	BUILD_BUG_ON(sizeof(struct unix_skb_parms) > sizeof(skb->cb));
 	scm->fp = UNIXCB(skb).fp;
 	UNIXCB(skb).fp = NULL;
 


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