Merge branch 'fix-sctp-diag-locking-issues'

Stefan Wiehler says:

====================
Fix SCTP diag locking issues

- Hold RCU read lock while iterating over address list in
  inet_diag_msg_sctpaddrs_fill()
- Prevent TOCTOU out-of-bounds write
- Hold sock lock while iterating over address list in sctp_sock_dump_one()
====================

Link: https://patch.msgid.link/20251028161506.3294376-1-stefan.wiehler@nokia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/sctp/diag.c

@@ -73,19 +73,26 @@ static int inet_diag_msg_sctpladdrs_fill(struct sk_buff *skb,
 	struct nlattr *attr;
 	void *info = NULL;
 
+	rcu_read_lock();
 	list_for_each_entry_rcu(laddr, address_list, list)
 		addrcnt++;
+	rcu_read_unlock();
 
 	attr = nla_reserve(skb, INET_DIAG_LOCALS, addrlen * addrcnt);
 	if (!attr)
 		return -EMSGSIZE;
 
 	info = nla_data(attr);
+	rcu_read_lock();
 	list_for_each_entry_rcu(laddr, address_list, list) {
 		memcpy(info, &laddr->a, sizeof(laddr->a));
 		memset(info + sizeof(laddr->a), 0, addrlen - sizeof(laddr->a));
 		info += addrlen;
+
+		if (!--addrcnt)
+			break;
 	}
+	rcu_read_unlock();
 
 	return 0;
 }
@@ -223,14 +230,15 @@ struct sctp_comm_param {
 	bool net_admin;
 };
 
-static size_t inet_assoc_attr_size(struct sctp_association *asoc)
+static size_t inet_assoc_attr_size(struct sock *sk,
+				   struct sctp_association *asoc)
 {
 	int addrlen = sizeof(struct sockaddr_storage);
 	int addrcnt = 0;
 	struct sctp_sockaddr_entry *laddr;
 
 	list_for_each_entry_rcu(laddr, &asoc->base.bind_addr.address_list,
-				list)
+				list, lockdep_sock_is_held(sk))
 		addrcnt++;
 
 	return	  nla_total_size(sizeof(struct sctp_info))
@@ -256,11 +264,14 @@ static int sctp_sock_dump_one(struct sctp_endpoint *ep, struct sctp_transport *t
 	if (err)
 		return err;
 
-	rep = nlmsg_new(inet_assoc_attr_size(assoc), GFP_KERNEL);
-	if (!rep)
+	lock_sock(sk);
+
+	rep = nlmsg_new(inet_assoc_attr_size(sk, assoc), GFP_KERNEL);
+	if (!rep) {
+		release_sock(sk);
 		return -ENOMEM;
+	}
 
-	lock_sock(sk);
 	if (ep != assoc->ep) {
 		err = -EAGAIN;
 		goto out;