ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 351 insertions, 0 deletions

diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c
new file mode 100644
index 000000000..c12d5e1ee
--- /dev/null
+++ b/net/l2tp/l2tp_debugfs.c
@@ -0,0 +1,351 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* L2TP subsystem debugfs
+ *
+ * Copyright (c) 2010 Katalix Systems Ltd
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/hash.h>
+#include <linux/l2tp.h>
+#include <linux/in.h>
+#include <linux/etherdevice.h>
+#include <linux/spinlock.h>
+#include <linux/debugfs.h>
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/udp.h>
+#include <net/inet_common.h>
+#include <net/inet_hashtables.h>
+#include <net/tcp_states.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#include "l2tp_core.h"
+
+static struct dentry *rootdir;
+
+struct l2tp_dfs_seq_data {
+	struct net	*net;
+	netns_tracker	ns_tracker;
+	unsigned long tkey;		/* lookup key of current tunnel */
+	unsigned long skey;		/* lookup key of current session */
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_session *session;	/* NULL means get next tunnel */
+};
+
+static void l2tp_dfs_next_tunnel(struct l2tp_dfs_seq_data *pd)
+{
+	/* Drop reference taken during previous invocation */
+	if (pd->tunnel)
+		l2tp_tunnel_put(pd->tunnel);
+
+	pd->tunnel = l2tp_tunnel_get_next(pd->net, &pd->tkey);
+	pd->tkey++;
+}
+
+static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd)
+{
+	/* Drop reference taken during previous invocation */
+	if (pd->session)
+		l2tp_session_put(pd->session);
+
+	pd->session = l2tp_session_get_next(pd->net, pd->tunnel->sock,
+					    pd->tunnel->version,
+					    pd->tunnel->tunnel_id, &pd->skey);
+	pd->skey++;
+
+	if (!pd->session) {
+		pd->skey = 0;
+		l2tp_dfs_next_tunnel(pd);
+	}
+}
+
+static void *l2tp_dfs_seq_start(struct seq_file *m, loff_t *offs)
+{
+	struct l2tp_dfs_seq_data *pd = SEQ_START_TOKEN;
+	loff_t pos = *offs;
+
+	if (!pos)
+		goto out;
+
+	if (WARN_ON(!m->private)) {
+		pd = NULL;
+		goto out;
+	}
+	pd = m->private;
+
+	if (!pd->tunnel)
+		l2tp_dfs_next_tunnel(pd);
+	else
+		l2tp_dfs_next_session(pd);
+
+	/* NULL tunnel and session indicates end of list */
+	if (!pd->tunnel && !pd->session)
+		pd = NULL;
+
+out:
+	return pd;
+}
+
+static void *l2tp_dfs_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	return NULL;
+}
+
+static void l2tp_dfs_seq_stop(struct seq_file *p, void *v)
+{
+	struct l2tp_dfs_seq_data *pd = v;
+
+	if (!pd || pd == SEQ_START_TOKEN)
+		return;
+
+	/* Drop reference taken by last invocation of l2tp_dfs_next_session()
+	 * or l2tp_dfs_next_tunnel().
+	 */
+	if (pd->session) {
+		l2tp_session_put(pd->session);
+		pd->session = NULL;
+	}
+	if (pd->tunnel) {
+		l2tp_tunnel_put(pd->tunnel);
+		pd->tunnel = NULL;
+	}
+}
+
+static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v)
+{
+	struct l2tp_tunnel *tunnel = v;
+	struct l2tp_session *session;
+	int session_count = 0;
+
+	rcu_read_lock_bh();
+	list_for_each_entry_rcu(session, &tunnel->session_list, list) {
+		/* Session ID of zero is a dummy/reserved value used by pppol2tp */
+		if (session->session_id == 0)
+			continue;
+
+		session_count++;
+	}
+	rcu_read_unlock_bh();
+
+	seq_printf(m, "\nTUNNEL %u peer %u", tunnel->tunnel_id, tunnel->peer_tunnel_id);
+	if (tunnel->sock) {
+		struct inet_sock *inet = inet_sk(tunnel->sock);
+
+#if IS_ENABLED(CONFIG_IPV6)
+		if (tunnel->sock->sk_family == AF_INET6) {
+			const struct ipv6_pinfo *np = inet6_sk(tunnel->sock);
+
+			seq_printf(m, " from %pI6c to %pI6c\n",
+				   &np->saddr, &tunnel->sock->sk_v6_daddr);
+		}
+#endif
+		if (tunnel->sock->sk_family == AF_INET)
+			seq_printf(m, " from %pI4 to %pI4\n",
+				   &inet->inet_saddr, &inet->inet_daddr);
+
+		if (tunnel->encap == L2TP_ENCAPTYPE_UDP)
+			seq_printf(m, " source port %hu, dest port %hu\n",
+				   ntohs(inet->inet_sport), ntohs(inet->inet_dport));
+	}
+	seq_printf(m, " L2TPv%d, %s\n", tunnel->version,
+		   tunnel->encap == L2TP_ENCAPTYPE_UDP ? "UDP" :
+		   tunnel->encap == L2TP_ENCAPTYPE_IP ? "IP" :
+		   "");
+	seq_printf(m, " %d sessions, refcnt %d/%d\n", session_count,
+		   tunnel->sock ? refcount_read(&tunnel->sock->sk_refcnt) : 0,
+		   refcount_read(&tunnel->ref_count));
+	seq_printf(m, " %08x tx %ld/%ld/%ld rx %ld/%ld/%ld\n",
+		   0,
+		   atomic_long_read(&tunnel->stats.tx_packets),
+		   atomic_long_read(&tunnel->stats.tx_bytes),
+		   atomic_long_read(&tunnel->stats.tx_errors),
+		   atomic_long_read(&tunnel->stats.rx_packets),
+		   atomic_long_read(&tunnel->stats.rx_bytes),
+		   atomic_long_read(&tunnel->stats.rx_errors));
+}
+
+static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
+{
+	struct l2tp_session *session = v;
+
+	seq_printf(m, "  SESSION %u, peer %u, %s\n", session->session_id,
+		   session->peer_session_id,
+		   session->pwtype == L2TP_PWTYPE_ETH ? "ETH" :
+		   session->pwtype == L2TP_PWTYPE_PPP ? "PPP" :
+		   "");
+	if (session->send_seq || session->recv_seq)
+		seq_printf(m, "   nr %u, ns %u\n", session->nr, session->ns);
+	seq_printf(m, "   refcnt %d\n", refcount_read(&session->ref_count));
+	seq_printf(m, "   config 0/0/%c/%c/-/%s %08x %u\n",
+		   session->recv_seq ? 'R' : '-',
+		   session->send_seq ? 'S' : '-',
+		   session->lns_mode ? "LNS" : "LAC",
+		   0,
+		   jiffies_to_msecs(session->reorder_timeout));
+	seq_printf(m, "   offset 0 l2specific %hu/%d\n",
+		   session->l2specific_type, l2tp_get_l2specific_len(session));
+	if (session->cookie_len) {
+		seq_printf(m, "   cookie %02x%02x%02x%02x",
+			   session->cookie[0], session->cookie[1],
+			   session->cookie[2], session->cookie[3]);
+		if (session->cookie_len == 8)
+			seq_printf(m, "%02x%02x%02x%02x",
+				   session->cookie[4], session->cookie[5],
+				   session->cookie[6], session->cookie[7]);
+		seq_puts(m, "\n");
+	}
+	if (session->peer_cookie_len) {
+		seq_printf(m, "   peer cookie %02x%02x%02x%02x",
+			   session->peer_cookie[0], session->peer_cookie[1],
+			   session->peer_cookie[2], session->peer_cookie[3]);
+		if (session->peer_cookie_len == 8)
+			seq_printf(m, "%02x%02x%02x%02x",
+				   session->peer_cookie[4], session->peer_cookie[5],
+				   session->peer_cookie[6], session->peer_cookie[7]);
+		seq_puts(m, "\n");
+	}
+
+	seq_printf(m, "   %u/%u tx %ld/%ld/%ld rx %ld/%ld/%ld\n",
+		   session->nr, session->ns,
+		   atomic_long_read(&session->stats.tx_packets),
+		   atomic_long_read(&session->stats.tx_bytes),
+		   atomic_long_read(&session->stats.tx_errors),
+		   atomic_long_read(&session->stats.rx_packets),
+		   atomic_long_read(&session->stats.rx_bytes),
+		   atomic_long_read(&session->stats.rx_errors));
+
+	if (session->show)
+		session->show(m, session);
+}
+
+static int l2tp_dfs_seq_show(struct seq_file *m, void *v)
+{
+	struct l2tp_dfs_seq_data *pd = v;
+
+	/* display header on line 1 */
+	if (v == SEQ_START_TOKEN) {
+		seq_puts(m, "TUNNEL ID, peer ID from IP to IP\n");
+		seq_puts(m, " L2TPv2/L2TPv3, UDP/IP\n");
+		seq_puts(m, " sessions session-count, refcnt refcnt/sk->refcnt\n");
+		seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
+		seq_puts(m, "  SESSION ID, peer ID, PWTYPE\n");
+		seq_puts(m, "   refcnt cnt\n");
+		seq_puts(m, "   offset OFFSET l2specific TYPE/LEN\n");
+		seq_puts(m, "   [ cookie ]\n");
+		seq_puts(m, "   [ peer cookie ]\n");
+		seq_puts(m, "   config mtu/mru/rcvseq/sendseq/dataseq/lns debug reorderto\n");
+		seq_puts(m, "   nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
+		goto out;
+	}
+
+	if (!pd->session)
+		l2tp_dfs_seq_tunnel_show(m, pd->tunnel);
+	else
+		l2tp_dfs_seq_session_show(m, pd->session);
+
+out:
+	return 0;
+}
+
+static const struct seq_operations l2tp_dfs_seq_ops = {
+	.start		= l2tp_dfs_seq_start,
+	.next		= l2tp_dfs_seq_next,
+	.stop		= l2tp_dfs_seq_stop,
+	.show		= l2tp_dfs_seq_show,
+};
+
+static int l2tp_dfs_seq_open(struct inode *inode, struct file *file)
+{
+	struct l2tp_dfs_seq_data *pd;
+	struct seq_file *seq;
+	int rc = -ENOMEM;
+
+	pd = kzalloc_obj(*pd);
+	if (!pd)
+		goto out;
+
+	/* Derive the network namespace from the pid opening the
+	 * file.
+	 */
+	pd->net = get_net_ns_by_pid(current->pid);
+	if (IS_ERR(pd->net)) {
+		rc = PTR_ERR(pd->net);
+		goto err_free_pd;
+	}
+	netns_tracker_alloc(pd->net, &pd->ns_tracker, GFP_KERNEL);
+	rc = seq_open(file, &l2tp_dfs_seq_ops);
+	if (rc)
+		goto err_free_net;
+
+	seq = file->private_data;
+	seq->private = pd;
+
+out:
+	return rc;
+
+err_free_net:
+	put_net_track(pd->net, &pd->ns_tracker);
+err_free_pd:
+	kfree(pd);
+	goto out;
+}
+
+static int l2tp_dfs_seq_release(struct inode *inode, struct file *file)
+{
+	struct l2tp_dfs_seq_data *pd;
+	struct seq_file *seq;
+
+	seq = file->private_data;
+	pd = seq->private;
+	if (pd->session)
+		l2tp_session_put(pd->session);
+	if (pd->tunnel)
+		l2tp_tunnel_put(pd->tunnel);
+	if (pd->net)
+		put_net_track(pd->net, &pd->ns_tracker);
+	kfree(pd);
+	seq_release(inode, file);
+
+	return 0;
+}
+
+static const struct file_operations l2tp_dfs_fops = {
+	.owner		= THIS_MODULE,
+	.open		= l2tp_dfs_seq_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= l2tp_dfs_seq_release,
+};
+
+static int __init l2tp_debugfs_init(void)
+{
+	rootdir = debugfs_create_dir("l2tp", NULL);
+
+	debugfs_create_file("tunnels", 0600, rootdir, NULL, &l2tp_dfs_fops);
+
+	pr_info("L2TP debugfs support\n");
+
+	return 0;
+}
+
+static void __exit l2tp_debugfs_exit(void)
+{
+	debugfs_remove_recursive(rootdir);
+}
+
+module_init(l2tp_debugfs_init);
+module_exit(l2tp_debugfs_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
+MODULE_DESCRIPTION("L2TP debugfs driver");
+MODULE_VERSION("1.0");