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, 225 insertions, 0 deletions

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
new file mode 100644
index 000000000..96fd7dc6d
--- /dev/null
+++ b/net/ipv4/gre_demux.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	GRE over IPv4 demultiplexer driver
+ *
+ *	Authors: Dmitry Kozlov (xeb@mail.ru)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/if.h>
+#include <linux/icmp.h>
+#include <linux/kernel.h>
+#include <linux/kmod.h>
+#include <linux/skbuff.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/netdevice.h>
+#include <linux/if_tunnel.h>
+#include <linux/spinlock.h>
+#include <net/protocol.h>
+#include <net/gre.h>
+#include <net/erspan.h>
+
+#include <net/icmp.h>
+#include <net/route.h>
+#include <net/xfrm.h>
+
+static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
+
+int gre_add_protocol(const struct gre_protocol *proto, u8 version)
+{
+	if (version >= GREPROTO_MAX)
+		return -EINVAL;
+
+	return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
+		0 : -EBUSY;
+}
+EXPORT_SYMBOL_GPL(gre_add_protocol);
+
+int gre_del_protocol(const struct gre_protocol *proto, u8 version)
+{
+	int ret;
+
+	if (version >= GREPROTO_MAX)
+		return -EINVAL;
+
+	ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
+		0 : -EBUSY;
+
+	if (ret)
+		return ret;
+
+	synchronize_rcu();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gre_del_protocol);
+
+/* Fills in tpi and returns header length to be pulled.
+ * Note that caller must use pskb_may_pull() before pulling GRE header.
+ */
+int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
+		     bool *csum_err, __be16 proto, int nhs)
+{
+	const struct gre_base_hdr *greh;
+	__be32 *options;
+	int hdr_len;
+
+	if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr))))
+		return -EINVAL;
+
+	greh = (struct gre_base_hdr *)(skb->data + nhs);
+	if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
+		return -EINVAL;
+
+	gre_flags_to_tnl_flags(tpi->flags, greh->flags);
+	hdr_len = gre_calc_hlen(tpi->flags);
+
+	if (!pskb_may_pull(skb, nhs + hdr_len))
+		return -EINVAL;
+
+	greh = (struct gre_base_hdr *)(skb->data + nhs);
+	tpi->proto = greh->protocol;
+
+	options = (__be32 *)(greh + 1);
+	if (greh->flags & GRE_CSUM) {
+		if (!skb_checksum_simple_validate(skb)) {
+			skb_checksum_try_convert(skb, IPPROTO_GRE,
+						 null_compute_pseudo);
+		} else if (csum_err) {
+			*csum_err = true;
+			return -EINVAL;
+		}
+
+		options++;
+	}
+
+	if (greh->flags & GRE_KEY) {
+		tpi->key = *options;
+		options++;
+	} else {
+		tpi->key = 0;
+	}
+	if (unlikely(greh->flags & GRE_SEQ)) {
+		tpi->seq = *options;
+		options++;
+	} else {
+		tpi->seq = 0;
+	}
+	/* WCCP version 1 and 2 protocol decoding.
+	 * - Change protocol to IPv4/IPv6
+	 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
+	 */
+	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
+		u8 _val, *val;
+
+		val = skb_header_pointer(skb, nhs + hdr_len,
+					 sizeof(_val), &_val);
+		if (!val)
+			return -EINVAL;
+		tpi->proto = proto;
+		if ((*val & 0xF0) != 0x40)
+			hdr_len += 4;
+	}
+	tpi->hdr_len = hdr_len;
+
+	/* ERSPAN ver 1 and 2 protocol sets GRE key field
+	 * to 0 and sets the configured key in the
+	 * inner erspan header field
+	 */
+	if ((greh->protocol == htons(ETH_P_ERSPAN) && hdr_len != 4) ||
+	    greh->protocol == htons(ETH_P_ERSPAN2)) {
+		struct erspan_base_hdr *ershdr;
+
+		if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr)))
+			return -EINVAL;
+
+		ershdr = (struct erspan_base_hdr *)(skb->data + nhs + hdr_len);
+		tpi->key = cpu_to_be32(get_session_id(ershdr));
+	}
+
+	return hdr_len;
+}
+EXPORT_SYMBOL(gre_parse_header);
+
+static int gre_rcv(struct sk_buff *skb)
+{
+	const struct gre_protocol *proto;
+	u8 ver;
+	int ret;
+
+	if (!pskb_may_pull(skb, 12))
+		goto drop;
+
+	ver = skb->data[1]&0x7f;
+	if (ver >= GREPROTO_MAX)
+		goto drop;
+
+	rcu_read_lock();
+	proto = rcu_dereference(gre_proto[ver]);
+	if (!proto || !proto->handler)
+		goto drop_nohandler;
+	ret = proto->handler(skb);
+	rcu_read_unlock();
+	return ret;
+
+drop_nohandler:
+	rcu_read_unlock();
+	dev_core_stats_rx_nohandler_inc(skb->dev);
+	kfree_skb(skb);
+	return NET_RX_DROP;
+drop:
+	dev_core_stats_rx_dropped_inc(skb->dev);
+	kfree_skb(skb);
+	return NET_RX_DROP;
+}
+
+static int gre_err(struct sk_buff *skb, u32 info)
+{
+	const struct gre_protocol *proto;
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
+	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
+	int err = 0;
+
+	if (ver >= GREPROTO_MAX)
+		return -EINVAL;
+
+	rcu_read_lock();
+	proto = rcu_dereference(gre_proto[ver]);
+	if (proto && proto->err_handler)
+		proto->err_handler(skb, info);
+	else
+		err = -EPROTONOSUPPORT;
+	rcu_read_unlock();
+
+	return err;
+}
+
+static const struct net_protocol net_gre_protocol = {
+	.handler     = gre_rcv,
+	.err_handler = gre_err,
+};
+
+static int __init gre_init(void)
+{
+	pr_info("GRE over IPv4 demultiplexer driver\n");
+
+	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
+		pr_err("can't add protocol\n");
+		return -EAGAIN;
+	}
+	return 0;
+}
+
+static void __exit gre_exit(void)
+{
+	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
+}
+
+module_init(gre_init);
+module_exit(gre_exit);
+
+MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
+MODULE_AUTHOR("D. Kozlov <xeb@mail.ru>");
+MODULE_LICENSE("GPL");