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, 134 insertions, 0 deletions

diff --git a/net/sched/em_ipset.c b/net/sched/em_ipset.c
new file mode 100644
index 000000000..c95cf86fb
--- /dev/null
+++ b/net/sched/em_ipset.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * net/sched/em_ipset.c	ipset ematch
+ *
+ * Copyright (c) 2012 Florian Westphal <fw@strlen.de>
+ */
+
+#include <linux/gfp.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <linux/netfilter/xt_set.h>
+#include <linux/ipv6.h>
+#include <net/ip.h>
+#include <net/pkt_cls.h>
+
+static int em_ipset_change(struct net *net, void *data, int data_len,
+			   struct tcf_ematch *em)
+{
+	struct xt_set_info *set = data;
+	ip_set_id_t index;
+
+	if (data_len != sizeof(*set))
+		return -EINVAL;
+
+	index = ip_set_nfnl_get_byindex(net, set->index);
+	if (index == IPSET_INVALID_ID)
+		return -ENOENT;
+
+	em->datalen = sizeof(*set);
+	em->data = (unsigned long)kmemdup(data, em->datalen, GFP_KERNEL);
+	if (em->data)
+		return 0;
+
+	ip_set_nfnl_put(net, index);
+	return -ENOMEM;
+}
+
+static void em_ipset_destroy(struct tcf_ematch *em)
+{
+	const struct xt_set_info *set = (const void *) em->data;
+	if (set) {
+		ip_set_nfnl_put(em->net, set->index);
+		kfree((void *) em->data);
+	}
+}
+
+static int em_ipset_match(struct sk_buff *skb, struct tcf_ematch *em,
+			  struct tcf_pkt_info *info)
+{
+	struct ip_set_adt_opt opt;
+	struct xt_action_param acpar;
+	const struct xt_set_info *set = (const void *) em->data;
+	struct net_device *dev, *indev = NULL;
+	struct nf_hook_state state = {
+		.net	= em->net,
+	};
+	int ret, network_offset;
+
+	switch (skb_protocol(skb, true)) {
+	case htons(ETH_P_IP):
+		state.pf = NFPROTO_IPV4;
+		if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
+			return 0;
+		acpar.thoff = ip_hdrlen(skb);
+		break;
+	case htons(ETH_P_IPV6):
+		state.pf = NFPROTO_IPV6;
+		if (!pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))
+			return 0;
+		/* doesn't call ipv6_find_hdr() because ipset doesn't use thoff, yet */
+		acpar.thoff = sizeof(struct ipv6hdr);
+		break;
+	default:
+		return 0;
+	}
+
+	opt.family = state.pf;
+	opt.dim = set->dim;
+	opt.flags = set->flags;
+	opt.cmdflags = 0;
+	opt.ext.timeout = ~0u;
+
+	network_offset = skb_network_offset(skb);
+	skb_pull(skb, network_offset);
+
+	dev = skb->dev;
+
+	rcu_read_lock();
+
+	if (skb->skb_iif)
+		indev = dev_get_by_index_rcu(em->net, skb->skb_iif);
+
+	state.in      = indev ? indev : dev;
+	state.out     = dev;
+	acpar.state   = &state;
+
+	ret = ip_set_test(set->index, skb, &acpar, &opt);
+
+	rcu_read_unlock();
+
+	skb_push(skb, network_offset);
+	return ret;
+}
+
+static struct tcf_ematch_ops em_ipset_ops = {
+	.kind	  = TCF_EM_IPSET,
+	.change	  = em_ipset_change,
+	.destroy  = em_ipset_destroy,
+	.match	  = em_ipset_match,
+	.owner	  = THIS_MODULE,
+	.link	  = LIST_HEAD_INIT(em_ipset_ops.link)
+};
+
+static int __init init_em_ipset(void)
+{
+	return tcf_em_register(&em_ipset_ops);
+}
+
+static void __exit exit_em_ipset(void)
+{
+	tcf_em_unregister(&em_ipset_ops);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
+MODULE_DESCRIPTION("TC extended match for IP sets");
+
+module_init(init_em_ipset);
+module_exit(exit_em_ipset);
+
+MODULE_ALIAS_TCF_EMATCH(TCF_EM_IPSET);