net: inet: Support UID-based routing in IP protocols.

- Use the UID in routing lookups made by protocol connect() and
  sendmsg() functions.
- Make sure that routing lookups triggered by incoming packets
  (e.g., Path MTU discovery) take the UID of the socket into
  account.
- For packets not associated with a userspace socket, (e.g., ping
  replies) use UID 0 inside the user namespace corresponding to
  the network namespace the socket belongs to. This allows
  all namespaces to apply routing and iptables rules to
  kernel-originated traffic in that namespaces by matching UID 0.
  This is better than using the UID of the kernel socket that is
  sending the traffic, because the UID of kernel sockets created
  at namespace creation time (e.g., the per-processor ICMP and
  TCP sockets) is the UID of the user that created the socket,
  which might not be mapped in the namespace.

Bug: 16355602
Change-Id: I910504b508948057912bc188fd1e8aca28294de3
Tested: compiles allnoconfig, allyesconfig, allmodconfig
Tested: https://android-review.googlesource.com/253302
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

[AmitP: A little bit of refactoring because of LTS cherry-pick commit
        e5abc10d19b9 ("tcp: fix NULL deref in tcp_v4_send_ack()")
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

4 files changed, 10 insertions, 5 deletions

diff --git a/include/net/flow.h b/include/net/flow.h
index 8913962d7d25..833080732dec 100644
--- a/include/net/flow.h
+++ b/include/net/flow.h
@@ -97,7 +97,8 @@ static inline void flowi4_init_output(struct flowi4 *fl4, int oif,
 				      __u32 mark, __u8 tos, __u8 scope,
 				      __u8 proto, __u8 flags,
 				      __be32 daddr, __be32 saddr,
-				      __be16 dport, __be16 sport)
+				      __be16 dport, __be16 sport,
+				      kuid_t uid)
 {
 	fl4->flowi4_oif = oif;
 	fl4->flowi4_iif = LOOPBACK_IFINDEX;
@@ -108,6 +109,7 @@ static inline void flowi4_init_output(struct flowi4 *fl4, int oif,
 	fl4->flowi4_flags = flags;
 	fl4->flowi4_secid = 0;
 	fl4->flowi4_tun_key.tun_id = 0;
+	fl4->flowi4_uid = uid;
 	fl4->daddr = daddr;
 	fl4->saddr = saddr;
 	fl4->fl4_dport = dport;
diff --git a/include/net/ip.h b/include/net/ip.h
index b450d8653b30..f78c3a52529b 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -170,6 +170,7 @@ struct ip_reply_arg {
 				/* -1 if not needed */ 
 	int	    bound_dev_if;
 	u8  	    tos;
+	kuid_t	    uid;
 }; 
 
 #define IP_REPLY_ARG_NOSRCCHECK 1
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 295d291269e2..af0e8c081191 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -116,9 +116,10 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 		  const struct in6_addr *gwaddr);
 
 void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu, int oif,
-		     u32 mark);
+		     u32 mark, kuid_t uid);
 void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu);
-void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark);
+void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark,
+		  kuid_t uid);
 void ip6_redirect_no_header(struct sk_buff *skb, struct net *net, int oif,
 			    u32 mark);
 void ip6_sk_redirect(struct sk_buff *skb, struct sock *sk);
diff --git a/include/net/route.h b/include/net/route.h
index a3b9ef74a389..3adb9c724818 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -154,7 +154,7 @@ static inline struct rtable *ip_route_output_ports(struct net *net, struct flowi
 	flowi4_init_output(fl4, oif, sk ? sk->sk_mark : 0, tos,
 			   RT_SCOPE_UNIVERSE, proto,
 			   sk ? inet_sk_flowi_flags(sk) : 0,
-			   daddr, saddr, dport, sport);
+			   daddr, saddr, dport, sport, sock_net_uid(net, sk));
 	if (sk)
 		security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
 	return ip_route_output_flow(net, fl4, sk);
@@ -267,7 +267,8 @@ static inline void ip_route_connect_init(struct flowi4 *fl4, __be32 dst, __be32
 		flow_flags |= FLOWI_FLAG_ANYSRC;
 
 	flowi4_init_output(fl4, oif, sk->sk_mark, tos, RT_SCOPE_UNIVERSE,
-			   protocol, flow_flags, dst, src, dport, sport);
+			   protocol, flow_flags, dst, src, dport, sport,
+			   sk->sk_uid);
 }
 
 static inline struct rtable *ip_route_connect(struct flowi4 *fl4,