[PATCH 3.18 016/145] ipv6: tcp: add a missing tcp_v6_restore_cb()

Greg Kroah-Hartman
2017-04-16T10:51:46Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit ebf6c9cb23d7e56eec8575a88071dec97ad5c6e2 ]

Dmitry reported use-after-free in ip6_datagram_recv_specific_ctl()

A similar bug was fixed in commit 8ce48623f0cf ("ipv6: tcp: restore
IP6CB for pktoptions skbs"), but I missed another spot.

tcp_v6_syn_recv_sock() can indeed set np->pktoptions from ireq->pktopts

Fixes: 971f10eca186 ("tcp: better TCP_SKB_CB layout to reduce cache line misses")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/tcp_ipv6.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)

--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1049,6 +1049,16 @@ drop:
return 0; /* don't send reset */
}

+static void tcp_v6_restore_cb(struct sk_buff *skb)
+{
+ /* We need to move header back to the beginning if xfrm6_policy_check()
+ * and tcp_v6_fill_cb() are going to be called again.
+ * ip6_datagram_recv_specific_ctl() also expects IP6CB to be there.
+ */
+ memmove(IP6CB(skb), &TCP_SKB_CB(skb)->header.h6,
+ sizeof(struct inet6_skb_parm));
+}
+
static struct sock *tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct dst_entry *dst)
@@ -1180,8 +1190,10 @@ static struct sock *tcp_v6_syn_recv_sock
sk_gfp_atomic(sk, GFP_ATOMIC));
consume_skb(ireq->pktopts);
ireq->pktopts = NULL;
- if (newnp->pktoptions)
+ if (newnp->pktoptions) {
+ tcp_v6_restore_cb(newnp->pktoptions);
skb_set_owner_r(newnp->pktoptions, newsk);
+ }
}
newnp->opt = NULL;
newnp->mcast_oif = tcp_v6_iif(skb);
@@ -1250,16 +1262,6 @@ out:
return NULL;
}

-static void tcp_v6_restore_cb(struct sk_buff *skb)
-{
- /* We need to move header back to the beginning if xfrm6_policy_check()
- * and tcp_v6_fill_cb() are going to be called again.
- * ip6_datagram_recv_specific_ctl() also expects IP6CB to be there.
- */
- memmove(IP6CB(skb), &TCP_SKB_CB(skb)->header.h6,
- sizeof(struct inet6_skb_parm));
-}
-
/* The socket must have it's spinlock held when we get
* here.
*