net/sock: add an explicit sk argument for ip_cmsg_recv_offset()

So that we can use it even after orphaining the skbuff.
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip.h

@@ -579,7 +579,8 @@ int ip_options_rcv_srr(struct sk_buff *skb);
  */
 
 void ipv4_pktinfo_prepare(const struct sock *sk, struct sk_buff *skb);
-void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb, int tlen, int offset);
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
+			 struct sk_buff *skb, int tlen, int offset);
 int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
 		 struct ipcm_cookie *ipc, bool allow_ipv6);
 int ip_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
@@ -601,7 +602,7 @@ void ip_local_error(struct sock *sk, int err, __be32 daddr, __be16 dport,
 
 static inline void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
 {
-	ip_cmsg_recv_offset(msg, skb, 0, 0);
+	ip_cmsg_recv_offset(msg, skb->sk, skb, 0, 0);
 }
 
 bool icmp_global_allow(void);

net/ipv4/ip_sockglue.c

@@ -164,10 +164,10 @@ static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)
 	put_cmsg(msg, SOL_IP, IP_ORIGDSTADDR, sizeof(sin), &sin);
 }
 
-void ip_cmsg_recv_offset(struct msghdr *msg, struct sk_buff *skb,
-			 int tlen, int offset)
+void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
+			 struct sk_buff *skb, int tlen, int offset)
 {
-	struct inet_sock *inet = inet_sk(skb->sk);
+	struct inet_sock *inet = inet_sk(sk);
 	unsigned int flags = inet->cmsg_flags;
 
 	/* Ordered by supposed usage frequency */

net/ipv4/udp.c

@@ -1421,7 +1421,7 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 		*addr_len = sizeof(*sin);
 	}
 	if (inet->cmsg_flags)
-		ip_cmsg_recv_offset(msg, skb, sizeof(struct udphdr), off);
+		ip_cmsg_recv_offset(msg, sk, skb, sizeof(struct udphdr), off);
 
 	err = copied;
 	if (flags & MSG_TRUNC)

net/ipv6/udp.c

@@ -425,7 +425,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 
 	if (is_udp4) {
 		if (inet->cmsg_flags)
-			ip_cmsg_recv_offset(msg, skb,
+			ip_cmsg_recv_offset(msg, sk, skb,
 					    sizeof(struct udphdr), off);
 	} else {
 		if (np->rxopt.all)