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, 306 insertions, 0 deletions

diff --git a/net/ipv6/tunnel6.c b/net/ipv6/tunnel6.c
new file mode 100644
index 000000000..dc4ea9b11
--- /dev/null
+++ b/net/ipv6/tunnel6.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C)2003,2004 USAGI/WIDE Project
+ *
+ * Authors	Mitsuru KANDA  <mk@linux-ipv6.org>
+ *		YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
+ */
+
+#define pr_fmt(fmt) "IPv6: " fmt
+
+#include <linux/icmpv6.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <net/ipv6.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+
+static struct xfrm6_tunnel __rcu *tunnel6_handlers __read_mostly;
+static struct xfrm6_tunnel __rcu *tunnel46_handlers __read_mostly;
+static struct xfrm6_tunnel __rcu *tunnelmpls6_handlers __read_mostly;
+static DEFINE_MUTEX(tunnel6_mutex);
+
+static inline int xfrm6_tunnel_mpls_supported(void)
+{
+	return IS_ENABLED(CONFIG_MPLS);
+}
+
+int xfrm6_tunnel_register(struct xfrm6_tunnel *handler, unsigned short family)
+{
+	struct xfrm6_tunnel __rcu **pprev;
+	struct xfrm6_tunnel *t;
+	int ret = -EEXIST;
+	int priority = handler->priority;
+
+	mutex_lock(&tunnel6_mutex);
+
+	switch (family) {
+	case AF_INET6:
+		pprev = &tunnel6_handlers;
+		break;
+	case AF_INET:
+		pprev = &tunnel46_handlers;
+		break;
+	case AF_MPLS:
+		pprev = &tunnelmpls6_handlers;
+		break;
+	default:
+		goto err;
+	}
+
+	for (; (t = rcu_dereference_protected(*pprev,
+			lockdep_is_held(&tunnel6_mutex))) != NULL;
+	     pprev = &t->next) {
+		if (t->priority > priority)
+			break;
+		if (t->priority == priority)
+			goto err;
+	}
+
+	handler->next = *pprev;
+	rcu_assign_pointer(*pprev, handler);
+
+	ret = 0;
+
+err:
+	mutex_unlock(&tunnel6_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(xfrm6_tunnel_register);
+
+int xfrm6_tunnel_deregister(struct xfrm6_tunnel *handler, unsigned short family)
+{
+	struct xfrm6_tunnel __rcu **pprev;
+	struct xfrm6_tunnel *t;
+	int ret = -ENOENT;
+
+	mutex_lock(&tunnel6_mutex);
+
+	switch (family) {
+	case AF_INET6:
+		pprev = &tunnel6_handlers;
+		break;
+	case AF_INET:
+		pprev = &tunnel46_handlers;
+		break;
+	case AF_MPLS:
+		pprev = &tunnelmpls6_handlers;
+		break;
+	default:
+		goto err;
+	}
+
+	for (; (t = rcu_dereference_protected(*pprev,
+			lockdep_is_held(&tunnel6_mutex))) != NULL;
+	     pprev = &t->next) {
+		if (t == handler) {
+			*pprev = handler->next;
+			ret = 0;
+			break;
+		}
+	}
+
+err:
+	mutex_unlock(&tunnel6_mutex);
+
+	synchronize_net();
+
+	return ret;
+}
+EXPORT_SYMBOL(xfrm6_tunnel_deregister);
+
+#define for_each_tunnel_rcu(head, handler)		\
+	for (handler = rcu_dereference(head);		\
+	     handler != NULL;				\
+	     handler = rcu_dereference(handler->next))	\
+
+static int tunnelmpls6_rcv(struct sk_buff *skb)
+{
+	struct xfrm6_tunnel *handler;
+
+	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+		goto drop;
+
+	for_each_tunnel_rcu(tunnelmpls6_handlers, handler)
+		if (!handler->handler(skb))
+			return 0;
+
+	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
+
+drop:
+	kfree_skb(skb);
+	return 0;
+}
+
+static int tunnel6_rcv(struct sk_buff *skb)
+{
+	struct xfrm6_tunnel *handler;
+
+	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+		goto drop;
+
+	for_each_tunnel_rcu(tunnel6_handlers, handler)
+		if (!handler->handler(skb))
+			return 0;
+
+	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
+
+drop:
+	kfree_skb(skb);
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
+static int tunnel6_rcv_cb(struct sk_buff *skb, u8 proto, int err)
+{
+	struct xfrm6_tunnel __rcu *head;
+	struct xfrm6_tunnel *handler;
+	int ret;
+
+	head = (proto == IPPROTO_IPV6) ? tunnel6_handlers : tunnel46_handlers;
+
+	for_each_tunnel_rcu(head, handler) {
+		if (handler->cb_handler) {
+			ret = handler->cb_handler(skb, err);
+			if (ret <= 0)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
+static const struct xfrm_input_afinfo tunnel6_input_afinfo = {
+	.family		=	AF_INET6,
+	.is_ipip	=	true,
+	.callback	=	tunnel6_rcv_cb,
+};
+#endif
+
+static int tunnel46_rcv(struct sk_buff *skb)
+{
+	struct xfrm6_tunnel *handler;
+
+	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+		goto drop;
+
+	for_each_tunnel_rcu(tunnel46_handlers, handler)
+		if (!handler->handler(skb))
+			return 0;
+
+	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
+
+drop:
+	kfree_skb(skb);
+	return 0;
+}
+
+static int tunnel6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+			u8 type, u8 code, int offset, __be32 info)
+{
+	struct xfrm6_tunnel *handler;
+
+	for_each_tunnel_rcu(tunnel6_handlers, handler)
+		if (!handler->err_handler(skb, opt, type, code, offset, info))
+			return 0;
+
+	return -ENOENT;
+}
+
+static int tunnel46_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+			 u8 type, u8 code, int offset, __be32 info)
+{
+	struct xfrm6_tunnel *handler;
+
+	for_each_tunnel_rcu(tunnel46_handlers, handler)
+		if (!handler->err_handler(skb, opt, type, code, offset, info))
+			return 0;
+
+	return -ENOENT;
+}
+
+static int tunnelmpls6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
+			   u8 type, u8 code, int offset, __be32 info)
+{
+	struct xfrm6_tunnel *handler;
+
+	for_each_tunnel_rcu(tunnelmpls6_handlers, handler)
+		if (!handler->err_handler(skb, opt, type, code, offset, info))
+			return 0;
+
+	return -ENOENT;
+}
+
+static const struct inet6_protocol tunnel6_protocol = {
+	.handler	= tunnel6_rcv,
+	.err_handler	= tunnel6_err,
+	.flags          = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
+};
+
+static const struct inet6_protocol tunnel46_protocol = {
+	.handler	= tunnel46_rcv,
+	.err_handler	= tunnel46_err,
+	.flags          = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
+};
+
+static const struct inet6_protocol tunnelmpls6_protocol = {
+	.handler	= tunnelmpls6_rcv,
+	.err_handler	= tunnelmpls6_err,
+	.flags          = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
+};
+
+static int __init tunnel6_init(void)
+{
+	if (inet6_add_protocol(&tunnel6_protocol, IPPROTO_IPV6)) {
+		pr_err("%s: can't add protocol\n", __func__);
+		return -EAGAIN;
+	}
+	if (inet6_add_protocol(&tunnel46_protocol, IPPROTO_IPIP)) {
+		pr_err("%s: can't add protocol\n", __func__);
+		inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6);
+		return -EAGAIN;
+	}
+	if (xfrm6_tunnel_mpls_supported() &&
+	    inet6_add_protocol(&tunnelmpls6_protocol, IPPROTO_MPLS)) {
+		pr_err("%s: can't add protocol\n", __func__);
+		inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6);
+		inet6_del_protocol(&tunnel46_protocol, IPPROTO_IPIP);
+		return -EAGAIN;
+	}
+#if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
+	if (xfrm_input_register_afinfo(&tunnel6_input_afinfo)) {
+		pr_err("%s: can't add input afinfo\n", __func__);
+		inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6);
+		inet6_del_protocol(&tunnel46_protocol, IPPROTO_IPIP);
+		if (xfrm6_tunnel_mpls_supported())
+			inet6_del_protocol(&tunnelmpls6_protocol, IPPROTO_MPLS);
+		return -EAGAIN;
+	}
+#endif
+	return 0;
+}
+
+static void __exit tunnel6_fini(void)
+{
+#if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
+	if (xfrm_input_unregister_afinfo(&tunnel6_input_afinfo))
+		pr_err("%s: can't remove input afinfo\n", __func__);
+#endif
+	if (inet6_del_protocol(&tunnel46_protocol, IPPROTO_IPIP))
+		pr_err("%s: can't remove protocol\n", __func__);
+	if (inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6))
+		pr_err("%s: can't remove protocol\n", __func__);
+	if (xfrm6_tunnel_mpls_supported() &&
+	    inet6_del_protocol(&tunnelmpls6_protocol, IPPROTO_MPLS))
+		pr_err("%s: can't remove protocol\n", __func__);
+}
+
+module_init(tunnel6_init);
+module_exit(tunnel6_fini);
+MODULE_DESCRIPTION("IP-in-IPv6 tunnel driver");
+MODULE_LICENSE("GPL");