[PATCH 4.4 02/27] ipsec: Fix aborted xfrm policy dump crash

Greg Kroah-Hartman
2017-12-04T16:00:12Z

From: Herbert Xu <herbert@gondor.apana.org.au>

commit 1137b5e2529a8f5ca8ee709288ecba3e68044df2 upstream.

An independent security researcher, Mohamed Ghannam, has reported
this vulnerability to Beyond Security's SecuriTeam Secure Disclosure
program.

The xfrm_dump_policy_done function expects xfrm_dump_policy to
have been called at least once or it will crash. This can be
triggered if a dump fails because the target socket's receive
buffer is full.

This patch fixes it by using the cb->start mechanism to ensure that
the initialisation is always done regardless of the buffer situation.

Fixes: 12a169e7d8f4 ("ipsec: Put dumpers on the dump list")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/xfrm/xfrm_user.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1652,32 +1652,34 @@ static int dump_one_policy(struct xfrm_p

static int xfrm_dump_policy_done(struct netlink_callback *cb)
{
- struct xfrm_policy_walk *walk = (struct xfrm_policy_walk *) &cb->args[1];
+ struct xfrm_policy_walk *walk = (struct xfrm_policy_walk *)cb->args;
struct net *net = sock_net(cb->skb->sk);

xfrm_policy_walk_done(walk, net);
return 0;
}

+static int xfrm_dump_policy_start(struct netlink_callback *cb)
+{
+ struct xfrm_policy_walk *walk = (struct xfrm_policy_walk *)cb->args;
+
+ BUILD_BUG_ON(sizeof(*walk) > sizeof(cb->args));
+
+ xfrm_policy_walk_init(walk, XFRM_POLICY_TYPE_ANY);
+ return 0;
+}
+
static int xfrm_dump_policy(struct sk_buff *skb, struct netlink_callback *cb)
{
struct net *net = sock_net(skb->sk);
- struct xfrm_policy_walk *walk = (struct xfrm_policy_walk *) &cb->args[1];
+ struct xfrm_policy_walk *walk = (struct xfrm_policy_walk *)cb->args;
struct xfrm_dump_info info;

- BUILD_BUG_ON(sizeof(struct xfrm_policy_walk) >
- sizeof(cb->args) - sizeof(cb->args[0]));
-
info.in_skb = cb->skb;
info.out_skb = skb;
info.nlmsg_seq = cb->nlh->nlmsg_seq;
info.nlmsg_flags = NLM_F_MULTI;

- if (!cb->args[0]) {
- cb->args[0] = 1;
- xfrm_policy_walk_init(walk, XFRM_POLICY_TYPE_ANY);
- }
-
(void) xfrm_policy_walk(net, walk, dump_one_policy, &info);

return skb->len;
@@ -2415,6 +2417,7 @@ static const struct nla_policy xfrma_spd

static const struct xfrm_link {
int (*doit)(struct sk_buff *, struct nlmsghdr *, struct nlattr **);
+ int (*start)(struct netlink_callback *);
int (*dump)(struct sk_buff *, struct netlink_callback *);
int (*done)(struct netlink_callback *);
const struct nla_policy *nla_pol;
@@ -2428,6 +2431,7 @@ static const struct xfrm_link {
[XFRM_MSG_NEWPOLICY - XFRM_MSG_BASE] = { .doit = xfrm_add_policy },
[XFRM_MSG_DELPOLICY - XFRM_MSG_BASE] = { .doit = xfrm_get_policy },
[XFRM_MSG_GETPOLICY - XFRM_MSG_BASE] = { .doit = xfrm_get_policy,
+ .start = xfrm_dump_policy_start,
.dump = xfrm_dump_policy,
.done = xfrm_dump_policy_done },
[XFRM_MSG_ALLOCSPI - XFRM_MSG_BASE] = { .doit = xfrm_alloc_userspi },
@@ -2479,6 +2483,7 @@ static int xfrm_user_rcv_msg(struct sk_b

{
struct netlink_dump_control c = {
+ .start = link->start,
.dump = link->dump,
.done = link->done,
};