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, 206 insertions, 0 deletions

diff --git a/net/ipv4/ipcomp.c b/net/ipv4/ipcomp.c
new file mode 100644
index 000000000..b1ea2d37e
--- /dev/null
+++ b/net/ipv4/ipcomp.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * IP Payload Compression Protocol (IPComp) - RFC3173.
+ *
+ * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
+ *
+ * Todo:
+ *   - Tunable compression parameters.
+ *   - Compression stats.
+ *   - Adaptive compression.
+ */
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/rtnetlink.h>
+#include <net/ip.h>
+#include <net/xfrm.h>
+#include <net/icmp.h>
+#include <net/ipcomp.h>
+#include <net/protocol.h>
+#include <net/sock.h>
+
+static int ipcomp4_err(struct sk_buff *skb, u32 info)
+{
+	struct net *net = dev_net(skb->dev);
+	__be32 spi;
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
+	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
+	struct xfrm_state *x;
+
+	switch (icmp_hdr(skb)->type) {
+	case ICMP_DEST_UNREACH:
+		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
+			return 0;
+		break;
+	case ICMP_REDIRECT:
+		break;
+	default:
+		return 0;
+	}
+
+	spi = htonl(ntohs(ipch->cpi));
+	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
+			      spi, IPPROTO_COMP, AF_INET);
+	if (!x)
+		return 0;
+
+	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
+		ipv4_update_pmtu(skb, net, info, 0, IPPROTO_COMP);
+	else
+		ipv4_redirect(skb, net, 0, IPPROTO_COMP);
+	xfrm_state_put(x);
+
+	return 0;
+}
+
+/* We always hold one tunnel user reference to indicate a tunnel */
+static struct lock_class_key xfrm_state_lock_key;
+static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
+{
+	struct net *net = xs_net(x);
+	struct xfrm_state *t;
+
+	t = xfrm_state_alloc(net);
+	if (!t)
+		goto out;
+	lockdep_set_class(&t->lock, &xfrm_state_lock_key);
+
+	t->id.proto = IPPROTO_IPIP;
+	t->id.spi = x->props.saddr.a4;
+	t->id.daddr.a4 = x->id.daddr.a4;
+	memcpy(&t->sel, &x->sel, sizeof(t->sel));
+	t->props.family = AF_INET;
+	t->props.mode = x->props.mode;
+	t->props.saddr.a4 = x->props.saddr.a4;
+	t->props.flags = x->props.flags;
+	t->props.extra_flags = x->props.extra_flags;
+	memcpy(&t->mark, &x->mark, sizeof(t->mark));
+	t->if_id = x->if_id;
+
+	if (xfrm_init_state(t, NULL))
+		goto error;
+
+	atomic_set(&t->tunnel_users, 1);
+out:
+	return t;
+
+error:
+	t->km.state = XFRM_STATE_DEAD;
+	xfrm_state_put(t);
+	t = NULL;
+	goto out;
+}
+
+/*
+ * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
+ * always incremented on success.
+ */
+static int ipcomp_tunnel_attach(struct xfrm_state *x)
+{
+	struct net *net = xs_net(x);
+	int err = 0;
+	struct xfrm_state *t;
+	u32 mark = x->mark.v & x->mark.m;
+
+	t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr.a4,
+			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
+	if (!t) {
+		t = ipcomp_tunnel_create(x);
+		if (!t) {
+			err = -EINVAL;
+			goto out;
+		}
+		xfrm_state_insert(t);
+		xfrm_state_hold(t);
+	}
+	x->tunnel = t;
+	atomic_inc(&t->tunnel_users);
+out:
+	return err;
+}
+
+static int ipcomp4_init_state(struct xfrm_state *x,
+			      struct netlink_ext_ack *extack)
+{
+	int err = -EINVAL;
+
+	x->props.header_len = 0;
+	switch (x->props.mode) {
+	case XFRM_MODE_TRANSPORT:
+		break;
+	case XFRM_MODE_TUNNEL:
+		x->props.header_len += sizeof(struct iphdr);
+		break;
+	default:
+		NL_SET_ERR_MSG(extack, "Unsupported XFRM mode for IPcomp");
+		goto out;
+	}
+
+	err = ipcomp_init_state(x, extack);
+	if (err)
+		goto out;
+
+	if (x->props.mode == XFRM_MODE_TUNNEL) {
+		err = ipcomp_tunnel_attach(x);
+		if (err) {
+			NL_SET_ERR_MSG(extack, "Kernel error: failed to initialize the associated state");
+			goto out;
+		}
+	}
+
+	err = 0;
+out:
+	return err;
+}
+
+static int ipcomp4_rcv_cb(struct sk_buff *skb, int err)
+{
+	return 0;
+}
+
+static const struct xfrm_type ipcomp_type = {
+	.owner		= THIS_MODULE,
+	.proto	     	= IPPROTO_COMP,
+	.init_state	= ipcomp4_init_state,
+	.destructor	= ipcomp_destroy,
+	.input		= ipcomp_input,
+	.output		= ipcomp_output
+};
+
+static struct xfrm4_protocol ipcomp4_protocol = {
+	.handler	=	xfrm4_rcv,
+	.input_handler	=	xfrm_input,
+	.cb_handler	=	ipcomp4_rcv_cb,
+	.err_handler	=	ipcomp4_err,
+	.priority	=	0,
+};
+
+static int __init ipcomp4_init(void)
+{
+	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
+		pr_info("%s: can't add xfrm type\n", __func__);
+		return -EAGAIN;
+	}
+	if (xfrm4_protocol_register(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
+		pr_info("%s: can't add protocol\n", __func__);
+		xfrm_unregister_type(&ipcomp_type, AF_INET);
+		return -EAGAIN;
+	}
+	return 0;
+}
+
+static void __exit ipcomp4_fini(void)
+{
+	if (xfrm4_protocol_deregister(&ipcomp4_protocol, IPPROTO_COMP) < 0)
+		pr_info("%s: can't remove protocol\n", __func__);
+	xfrm_unregister_type(&ipcomp_type, AF_INET);
+}
+
+module_init(ipcomp4_init);
+module_exit(ipcomp4_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp/IPv4) - RFC3173");
+MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
+
+MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);