[PATCH v1 net 3/5] tcp/udp: Call inet6_destroy_sock() in IPv4 sk_prot->destroy().

[Kuniyuki Iwashima <kuniyu@amazon.com>]

Originally, inet6_sk(sk)->XXX were changed under lock_sock(), so we were
able to clean them up by calling inet6_destroy_sock() during the IPv6 ->
IPv4 conversion by IPV6_ADDRFORM.  However, commit 03485f2adcde ("udpv6:
Add lockless sendmsg() support") added a lockless memory allocation path,
which could cause a memory leak:

setsockopt(IPV6_ADDRFORM)                 sendmsg()
+-----------------------+                 +-------+
- do_ipv6_setsockopt(sk, ...)             - udpv6_sendmsg(sk, ...)
  - lock_sock(sk)                           ^._ called via udpv6_prot
  - WRITE_ONCE(sk->sk_prot, &tcp_prot)          before WRITE_ONCE()
  - inet6_destroy_sock()
  - release_sock(sk)                        - ip6_make_skb(sk, ...)
                                              ^._ lockless fast path for
                                                  the non-corking case

                                              - __ip6_append_data(sk, ...)
                                                - ipv6_local_rxpmtu(sk, ...)
                                                  - xchg(&np->rxpmtu, skb)
                                                    ^._ rxpmtu is never freed.

                                            - lock_sock(sk)

For now, rxpmtu is only the case, but let's call inet6_destroy_sock()
in both TCP/UDP v4 destroy functions not to miss the future change.

We can consolidate TCP/UDP v4/v6 destroy functions, but such changes
are too invasive to backport to stable.  So, they can be posted as a
follow-up later for net-next.

Fixes: 03485f2adcde ("udpv6: Add lockless sendmsg() support")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
Cc: Vladislav Yasevich <vyasevic@redhat.com>
---
 net/ipv4/tcp_ipv4.c | 5 +++++
 net/ipv4/udp.c      | 6 ++++++
 net/ipv6/tcp_ipv6.c | 1 -
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5b019ba2b9d2..035b6c52a243 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2263,6 +2263,11 @@ void tcp_v4_destroy_sock(struct sock *sk)
 	tcp_saved_syn_free(tp);
 
 	sk_sockets_allocated_dec(sk);
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_prot_creator == &tcpv6_prot)
+		inet6_destroy_sock(sk);
+#endif
 }
 EXPORT_SYMBOL(tcp_v4_destroy_sock);
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 560d9eadeaa5..cdf131c0a819 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -115,6 +115,7 @@
 #include <net/udp_tunnel.h>
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6_stubs.h>
+#include <net/transp_v6.h>
 #endif
 
 struct udp_table udp_table __read_mostly;
@@ -2666,6 +2667,11 @@ void udp_destroy_sock(struct sock *sk)
 		if (up->encap_enabled)
 			static_branch_dec(&udp_encap_needed_key);
 	}
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_prot_creator == &udpv6_prot)
+		inet6_destroy_sock(sk);
+#endif
 }
 
 /*
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index e54eee80ce5f..1ff6a92f7774 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1945,7 +1945,6 @@ static int tcp_v6_init_sock(struct sock *sk)
 static void tcp_v6_destroy_sock(struct sock *sk)
 {
 	tcp_v4_destroy_sock(sk);
-	inet6_destroy_sock(sk);
 }
 
 #ifdef CONFIG_PROC_FS
-- 
2.30.2