[v2.6.34-stable 071/213] xfrm_user: return error pointer instead of NULL

From: Paul Gortmaker
Date: Wed Feb 05 2014 - 16:00:34 EST

From: Mathias Krause <minipli@xxxxxxxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 864745d291b5ba80ea0bd0edcbe67273de368836 upstream.

When dump_one_state() returns an error, e.g. because of a too small
buffer to dump the whole xfrm state, xfrm_state_netlink() returns NULL
instead of an error pointer. But its callers expect an error pointer
and therefore continue to operate on a NULL skbuff.

This could lead to a privilege escalation (execution of user code in
kernel context) if the attacker has CAP_NET_ADMIN and is able to map
address 0.

Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Acked-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
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 44d18db58cbb..bbc09e0c1ae7 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -765,6 +765,7 @@ static struct sk_buff *xfrm_state_netlink(struct sk_buff *in_skb,
struct xfrm_dump_info info;
struct sk_buff *skb;
+ int err;

if (!skb)
@@ -775,9 +776,10 @@ static struct sk_buff *xfrm_state_netlink(struct sk_buff *in_skb,
info.nlmsg_seq = seq;
info.nlmsg_flags = 0;

- if (dump_one_state(x, 0, &info)) {
+ err = dump_one_state(x, 0, &info);
+ if (err) {
- return NULL;
+ return ERR_PTR(err);

return skb;

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