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ipsec: Fix aborted xfrm policy dump crash

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: 12a169e ("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>
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herbertx authored and Steffen Klassert committed Oct 19, 2017
1 parent 10a7ef3 commit 1137b5e2529a8f5ca8ee709288ecba3e68044df2
Showing with 15 additions and 10 deletions.
  1. +15 −10 net/xfrm/xfrm_user.c
@@ -1693,32 +1693,34 @@ static int dump_one_policy(struct xfrm_policy *xp, int dir, int count, void *ptr

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;
@@ -2474,6 +2476,7 @@ static const struct nla_policy xfrma_spd_policy[XFRMA_SPD_MAX+1] = {

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;
@@ -2487,6 +2490,7 @@ 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 },
@@ -2539,6 +2543,7 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,

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

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