net: make skb_set_owner_w() more robust

skb_set_owner_w() is called from various places that assume
skb->sk always point to a full blown socket (as it changes
sk->sk_wmem_alloc)

We'd like to attach skb to request sockets, and in the future
to timewait sockets as well. For these kind of pseudo sockets,
we need to take a traditional refcount and use sock_edemux()
as the destructor.

It is now time to un-inline skb_set_owner_w(), being too big.

Fixes: ca6fb0651883 ("tcp: attach SYNACK messages to request sockets instead of listener")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Bisected-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 25 insertions, 18 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index aeed5c95f3ca..f570e75e3da9 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1951,6 +1951,8 @@ static inline void skb_set_hash_from_sk(struct sk_buff *skb, struct sock *sk)
         }
 }
 
+void skb_set_owner_w(struct sk_buff *skb, struct sock *sk);
+
 /*
  *      Queue a received datagram if it will fit. Stream and sequenced
  *      protocols can't normally use this as they need to fit buffers in
@@ -1959,21 +1961,6 @@ static inline void skb_set_hash_from_sk(struct sk_buff *skb, struct sock *sk)
  *      Inlined as it's very short and called for pretty much every
  *      packet ever received.
  */
-
-static inline void skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
-{
-        skb_orphan(skb);
-        skb->sk = sk;
-        skb->destructor = sock_wfree;
-        skb_set_hash_from_sk(skb, sk);
-        /*
-         * We used to take a refcount on sk, but following operation
-         * is enough to guarantee sk_free() wont free this sock until
-         * all in-flight packets are completed
-         */
-        atomic_add(skb->truesize, &sk->sk_wmem_alloc);
-}
-
 static inline void skb_set_owner_r(struct sk_buff *skb, struct sock *sk)
 {
         skb_orphan(skb);
diff --git a/net/core/sock.c b/net/core/sock.c
index 0ef30aa90132..7529eb9463be 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1656,6 +1656,28 @@ void sock_wfree(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(sock_wfree);
 
+void skb_set_owner_w(struct sk_buff *skb, struct sock *sk)
+{
+        skb_orphan(skb);
+        skb->sk = sk;
+#ifdef CONFIG_INET
+        if (unlikely(!sk_fullsock(sk))) {
+                skb->destructor = sock_edemux;
+                sock_hold(sk);
+                return;
+        }
+#endif
+        skb->destructor = sock_wfree;
+        skb_set_hash_from_sk(skb, sk);
+        /*
+         * We used to take a refcount on sk, but following operation
+         * is enough to guarantee sk_free() wont free this sock until
+         * all in-flight packets are completed
+         */
+        atomic_add(skb->truesize, &sk->sk_wmem_alloc);
+}
+EXPORT_SYMBOL(skb_set_owner_w);
+
 void skb_orphan_partial(struct sk_buff *skb)
 {
         /* TCP stack sets skb->ooo_okay based on sk_wmem_alloc,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f4f9793eb025..cb7ca569052c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2963,9 +2963,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
         skb_reserve(skb, MAX_TCP_HEADER);
 
         if (attach_req) {
-                skb->destructor = sock_edemux;
-                sock_hold(req_to_sk(req));
-                skb->sk = req_to_sk(req);
+                skb_set_owner_w(skb, req_to_sk(req));
         } else {
                 /* sk is a const pointer, because we want to express multiple
                  * cpu might call us concurrently.