sock: add sock_krfree_s helper

This patch adds the rcu version of sock_kfree_s() helper, named
sock_krfree_s(), to free the memory using kfree_rcu_mightsleep()
and adjust the socket's option memory buffer.

This new helper is first used in MPTCP.

Signed-off-by: Geliang Tang <[email protected]>

Author: geliangtang

include/net/sock.h

@@ -1836,6 +1836,7 @@ void *sock_kmemdup(struct sock *sk, const void *src,
 		   int size, gfp_t priority);
 void sock_kfree_s(struct sock *sk, void *mem, int size);
 void sock_kzfree_s(struct sock *sk, void *mem, int size);
+void sock_krfree_s(struct sock *sk, void *mem, int size);
 void sk_send_sigurg(struct sock *sk);
 
 static inline void sock_replace_proto(struct sock *sk, struct proto *proto)

net/core/sock.c

@@ -2862,29 +2862,37 @@ EXPORT_SYMBOL(sock_kmemdup);
  * condition entirely.
  */
 static inline void __sock_kfree_s(struct sock *sk, void *mem, int size,
-				  const bool nullify)
+				  const bool nullify, const bool rcu)
 {
 	if (WARN_ON_ONCE(!mem))
 		return;
 	if (nullify)
 		kfree_sensitive(mem);
+	else if (rcu)
+		kfree_rcu_mightsleep(mem);
 	else
 		kfree(mem);
 	atomic_sub(size, &sk->sk_omem_alloc);
 }
 
 void sock_kfree_s(struct sock *sk, void *mem, int size)
 {
-	__sock_kfree_s(sk, mem, size, false);
+	__sock_kfree_s(sk, mem, size, false, false);
 }
 EXPORT_SYMBOL(sock_kfree_s);
 
 void sock_kzfree_s(struct sock *sk, void *mem, int size)
 {
-	__sock_kfree_s(sk, mem, size, true);
+	__sock_kfree_s(sk, mem, size, true, false);
 }
 EXPORT_SYMBOL(sock_kzfree_s);
 
+void sock_krfree_s(struct sock *sk, void *mem, int size)
+{
+	__sock_kfree_s(sk, mem, size, false, true);
+}
+EXPORT_SYMBOL(sock_krfree_s);
+
 /* It is almost wait_for_tcp_memory minus release_sock/lock_sock.
    I think, these locks should be removed for datagram sockets.
  */

net/mptcp/pm_userspace.c

@@ -337,11 +337,10 @@ int mptcp_pm_nl_remove_doit(struct sk_buff *skb, struct genl_info *info)
 
 	release_sock(sk);
 
-	kfree_rcu_mightsleep(match);
 	/* Adjust sk_omem_alloc like sock_kfree_s() does, to match
 	 * with allocation of this memory by sock_kmemdup()
 	 */
-	atomic_sub(sizeof(*match), &sk->sk_omem_alloc);
+	sock_krfree_s(sk, match, sizeof(*match));
 
 	err = 0;
 out: