[PATCH] xfrm_user: return error pointer instead of NULL #2

When dump_one_policy() returns an error, e.g. because of a too small
buffer to dump the whole xfrm policy, xfrm_policy_netlink() returns
NULL instead of an error pointer. But its caller expects an error
pointer and therefore continues to operate on a NULL skbuff.

Cc: stable@vger.kernel.org
Signed-off-by: Mathias Krause <redacted>
---

Note, this is a different, but similar issue as my previous patch
with the almost same subject.

I'm not aware of a way how to exploit this bug as the policy *should*
always fit into the netlink buffer but better safe then sorry, so cc
stable.

 net/xfrm/xfrm_user.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index dac08e2..d12b625 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c

@@ -1548,6 +1548,7 @@ static struct sk_buff *xfrm_policy_netlink(struct sk_buff *in_skb,
 {
 	struct xfrm_dump_info info;
 	struct sk_buff *skb;
+	int err;
 
 	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (!skb)

@@ -1558,9 +1559,10 @@ static struct sk_buff *xfrm_policy_netlink(struct sk_buff *in_skb,
 	info.nlmsg_seq = seq;
 	info.nlmsg_flags = 0;
 
-	if (dump_one_policy(xp, dir, 0, &info) < 0) {
+	err = dump_one_policy(xp, dir, 0, &info);
+	if (err) {
 		kfree_skb(skb);
-		return NULL;
+		return ERR_PTR(err);
 	}
 
 	return skb;

-- 
1.7.10.4

On Fri, Sep 14, 2012 at 09:58:32PM +0200, Mathias Krause wrote:

When dump_one_policy() returns an error, e.g. because of a too small
buffer to dump the whole xfrm policy, xfrm_policy_netlink() returns
NULL instead of an error pointer. But its caller expects an error
pointer and therefore continues to operate on a NULL skbuff.

Cc: stable@vger.kernel.org
Signed-off-by: Mathias Krause <redacted>

Acked-by: Steffen Klassert <steffen.klassert@secunet.com>

From: Steffen Klassert <steffen.klassert@secunet.com>
Date: Mon, 17 Sep 2012 09:18:53 +0200

On Fri, Sep 14, 2012 at 09:58:32PM +0200, Mathias Krause wrote:

quoted

When dump_one_policy() returns an error, e.g. because of a too small
buffer to dump the whole xfrm policy, xfrm_policy_netlink() returns
NULL instead of an error pointer. But its caller expects an error
pointer and therefore continues to operate on a NULL skbuff.

Cc: stable@vger.kernel.org
Signed-off-by: Mathias Krause <redacted>

Acked-by: Steffen Klassert <steffen.klassert@secunet.com>

Applied and queued up for -stable.