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Subject[PATCH] xfrm_user: return error pointer instead of NULL
Date
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.

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

A test case can be provided on request.

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 e75d8e4..dac08e2 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -878,6 +878,7 @@ static struct sk_buff *xfrm_state_netlink(struct sk_buff *in_skb,
{
struct xfrm_dump_info info;
struct sk_buff *skb;
+ int err;

skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
if (!skb)
@@ -888,9 +889,10 @@ 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) {
kfree_skb(skb);
- return NULL;
+ return ERR_PTR(err);
}

return skb;
--
1.7.10.4


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