From 7b14e15ae6f4850392800482efb54d5cf4ae300c Mon Sep 17 00:00:00 2001
From: Jeremy Kerr <jk@codeconstruct.com.au>
Date: Wed, 29 Sep 2021 15:26:09 +0800
Subject: mctp: Implement a timeout for tags

Currently, a MCTP (local-eid,remote-eid,tag) tuple is allocated to a
socket on send, and only expires when the socket is closed.

This change introduces a tag timeout, freeing the tuple after a fixed
expiry - currently six seconds. This is greater than (but close to) the
max response timeout in upper-layer bindings.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/mctp/af_mctp.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 net/mctp/route.c   |  8 ++++++++
 2 files changed, 52 insertions(+)

(limited to 'net/mctp')

diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index 2767d548736b..46e5ede385cb 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -223,16 +223,60 @@ static const struct proto_ops mctp_dgram_ops = {
 	.sendpage	= sock_no_sendpage,
 };
 
+static void mctp_sk_expire_keys(struct timer_list *timer)
+{
+	struct mctp_sock *msk = container_of(timer, struct mctp_sock,
+					     key_expiry);
+	struct net *net = sock_net(&msk->sk);
+	unsigned long next_expiry, flags;
+	struct mctp_sk_key *key;
+	struct hlist_node *tmp;
+	bool next_expiry_valid = false;
+
+	spin_lock_irqsave(&net->mctp.keys_lock, flags);
+
+	hlist_for_each_entry_safe(key, tmp, &msk->keys, sklist) {
+		spin_lock(&key->lock);
+
+		if (!time_after_eq(key->expiry, jiffies)) {
+			key->valid = false;
+			hlist_del_rcu(&key->hlist);
+			hlist_del_rcu(&key->sklist);
+			spin_unlock(&key->lock);
+			mctp_key_unref(key);
+			continue;
+		}
+
+		if (next_expiry_valid) {
+			if (time_before(key->expiry, next_expiry))
+				next_expiry = key->expiry;
+		} else {
+			next_expiry = key->expiry;
+			next_expiry_valid = true;
+		}
+		spin_unlock(&key->lock);
+	}
+
+	spin_unlock_irqrestore(&net->mctp.keys_lock, flags);
+
+	if (next_expiry_valid)
+		mod_timer(timer, next_expiry);
+}
+
 static int mctp_sk_init(struct sock *sk)
 {
 	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
 
 	INIT_HLIST_HEAD(&msk->keys);
+	timer_setup(&msk->key_expiry, mctp_sk_expire_keys, 0);
 	return 0;
 }
 
 static void mctp_sk_close(struct sock *sk, long timeout)
 {
+	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
+
+	del_timer_sync(&msk->key_expiry);
 	sk_common_release(sk);
 }
 
diff --git a/net/mctp/route.c b/net/mctp/route.c
index 37aa67847a5a..c342adf4f97f 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -24,6 +24,8 @@
 #include <net/sock.h>
 
 static const unsigned int mctp_message_maxlen = 64 * 1024;
+static const unsigned long mctp_key_lifetime = 6 * CONFIG_HZ;
+
 
 /* route output callbacks */
 static int mctp_route_discard(struct mctp_route *route, struct sk_buff *skb)
@@ -175,6 +177,9 @@ static int mctp_key_add(struct mctp_sk_key *key, struct mctp_sock *msk)
 
 	if (!rc) {
 		refcount_inc(&key->refs);
+		key->expiry = jiffies + mctp_key_lifetime;
+		timer_reduce(&msk->key_expiry, key->expiry);
+
 		hlist_add_head(&key->hlist, &net->mctp.keys);
 		hlist_add_head(&key->sklist, &msk->keys);
 	}
@@ -497,6 +502,9 @@ static void mctp_reserve_tag(struct net *net, struct mctp_sk_key *key,
 
 	lockdep_assert_held(&mns->keys_lock);
 
+	key->expiry = jiffies + mctp_key_lifetime;
+	timer_reduce(&msk->key_expiry, key->expiry);
+
 	/* we hold the net->key_lock here, allowing updates to both
 	 * then net and sk
 	 */
-- 
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