4 files changed, 51 insertions, 6 deletions

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 984050f35c61..01bea76e3891 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -60,10 +60,38 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct net_device *dev = dst->dev;
+	unsigned int hh_len = LL_RESERVED_SPACE(dev);
+	int delta = hh_len - skb_headroom(skb);
 	const struct in6_addr *nexthop;
 	struct neighbour *neigh;
 	int ret;
 
+	/* Be paranoid, rather than too clever. */
+	if (unlikely(delta > 0) && dev->header_ops) {
+		/* pskb_expand_head() might crash, if skb is shared */
+		if (skb_shared(skb)) {
+			struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
+
+			if (likely(nskb)) {
+				if (skb->sk)
+					skb_set_owner_w(skb, skb->sk);
+				consume_skb(skb);
+			} else {
+				kfree_skb(skb);
+			}
+			skb = nskb;
+		}
+		if (skb &&
+		    pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
+			kfree_skb(skb);
+			skb = NULL;
+		}
+		if (!skb) {
+			IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTDISCARDS);
+			return -ENOMEM;
+		}
+	}
+
 	if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) {
 		struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));
 
@@ -479,7 +507,9 @@ int ip6_forward(struct sk_buff *skb)
 	if (skb_warn_if_lro(skb))
 		goto drop;
 
-	if (!xfrm6_policy_check(NULL, XFRM_POLICY_FWD, skb)) {
+	if (!net->ipv6.devconf_all->disable_policy &&
+	    !idev->cnf.disable_policy &&
+	    !xfrm6_policy_check(NULL, XFRM_POLICY_FWD, skb)) {
 		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 		goto drop;
 	}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 578ab6305c3f..0ce52d46e4f8 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -348,11 +348,20 @@ failure:
 static void tcp_v6_mtu_reduced(struct sock *sk)
 {
 	struct dst_entry *dst;
+	u32 mtu;
 
 	if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
 		return;
 
-	dst = inet6_csk_update_pmtu(sk, tcp_sk(sk)->mtu_info);
+	mtu = READ_ONCE(tcp_sk(sk)->mtu_info);
+
+	/* Drop requests trying to increase our current mss.
+	 * Check done in __ip6_rt_update_pmtu() is too late.
+	 */
+	if (tcp_mtu_to_mss(sk, mtu) >= tcp_sk(sk)->mss_cache)
+		return;
+
+	dst = inet6_csk_update_pmtu(sk, mtu);
 	if (!dst)
 		return;
 
@@ -433,6 +442,8 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	}
 
 	if (type == ICMPV6_PKT_TOOBIG) {
+		u32 mtu = ntohl(info);
+
 		/* We are not interested in TCP_LISTEN and open_requests
 		 * (SYN-ACKs send out by Linux are always <576bytes so
 		 * they should go through unfragmented).
@@ -443,7 +454,11 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		if (!ip6_sk_accept_pmtu(sk))
 			goto out;
 
-		tp->mtu_info = ntohl(info);
+		if (mtu < IPV6_MIN_MTU)
+			goto out;
+
+		WRITE_ONCE(tp->mtu_info, mtu);
+
 		if (!sock_owned_by_user(sk))
 			tcp_v6_mtu_reduced(sk);
 		else if (!test_and_set_bit(TCP_MTU_REDUCED_DEFERRED,
@@ -540,7 +555,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
 		opt = ireq->ipv6_opt;
 		if (!opt)
 			opt = rcu_dereference(np->opt);
-		err = ip6_xmit(sk, skb, fl6, sk->sk_mark, opt,
+		err = ip6_xmit(sk, skb, fl6, skb->mark ? : sk->sk_mark, opt,
 			       tclass, sk->sk_priority);
 		rcu_read_unlock();
 		err = net_xmit_eval(err);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 368972dbd919..0cc7ba531b34 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1296,7 +1296,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);
 
 	ipcm6_init(&ipc6);
-	ipc6.gso_size = up->gso_size;
+	ipc6.gso_size = READ_ONCE(up->gso_size);
 	ipc6.sockc.tsflags = sk->sk_tsflags;
 	ipc6.sockc.mark = sk->sk_mark;
 
diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index 57fa27c1cdf9..d0d280077721 100644
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -49,7 +49,7 @@ static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb_dst(skb);
 	struct xfrm_state *x = dst->xfrm;
-	int mtu;
+	unsigned int mtu;
 	bool toobig;
 
 #ifdef CONFIG_NETFILTER