mptcp: pm: Defer freeing of MPTCP userspace path manager entries

When path manager entries are deleted from the local address list, they
are first unlinked from the address list using list_del_rcu(). The
entries must not be freed until after the RCU grace period, but the
existing code immediately frees the entry.

Use kfree_rcu_mightsleep() and adjust sk_omem_alloc in open code instead
of using the sock_kfree_s() helper. This code path is only called in a
netlink handler, so the "might sleep" function is preferable to adding
a rarely-used rcu_head member to struct mptcp_pm_addr_entry.

Signed-off-by: Mat Martineau <[email protected]>

Author: mjmartineau

net/mptcp/pm_userspace.c

@@ -337,7 +337,8 @@ int mptcp_pm_nl_remove_doit(struct sk_buff *skb, struct genl_info *info)
 
 	release_sock(sk);
 
-	sock_kfree_s(sk, match, sizeof(*match));
+	kfree_rcu_mightsleep(match);
+	atomic_sub(sizeof(*match), &sk->sk_omem_alloc);
 
 	err = 0;
 out: