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, 194 insertions, 0 deletions

diff --git a/net/x25/x25_dev.c b/net/x25/x25_dev.c
new file mode 100644
index 000000000..fb8ac1aa5
--- /dev/null
+++ b/net/x25/x25_dev.c
@@ -0,0 +1,194 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine, randomly fail to work with new
+ *	releases, misbehave and/or generally screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	Started coding.
+ *      2000-09-04	Henner Eisen	Prevent freeing a dangling skb.
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <net/sock.h>
+#include <linux/if_arp.h>
+#include <net/x25.h>
+#include <net/x25device.h>
+
+static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
+{
+	struct sock *sk;
+	unsigned short frametype;
+	unsigned int lci;
+
+	if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+		return 0;
+
+	frametype = skb->data[2];
+	lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
+
+	/*
+	 *	LCI of zero is always for us, and its always a link control
+	 *	frame.
+	 */
+	if (lci == 0) {
+		x25_link_control(skb, nb, frametype);
+		return 0;
+	}
+
+	/*
+	 *	Find an existing socket.
+	 */
+	if ((sk = x25_find_socket(lci, nb)) != NULL) {
+		int queued = 1;
+
+		skb_reset_transport_header(skb);
+		bh_lock_sock(sk);
+		if (!sock_owned_by_user(sk)) {
+			queued = x25_process_rx_frame(sk, skb);
+		} else {
+			queued = !sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf));
+		}
+		bh_unlock_sock(sk);
+		sock_put(sk);
+		return queued;
+	}
+
+	/*
+	 *	Is is a Call Request ? if so process it.
+	 */
+	if (frametype == X25_CALL_REQUEST)
+		return x25_rx_call_request(skb, nb, lci);
+
+	/*
+	 * 	Its not a Call Request, nor is it a control frame.
+	 *	Can we forward it?
+	 */
+
+	if (x25_forward_data(lci, nb, skb)) {
+		if (frametype == X25_CLEAR_CONFIRMATION) {
+			x25_clear_forward_by_lci(lci);
+		}
+		kfree_skb(skb);
+		return 1;
+	}
+
+/*
+	x25_transmit_clear_request(nb, lci, 0x0D);
+*/
+
+	if (frametype != X25_CLEAR_CONFIRMATION)
+		pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype);
+
+	return 0;
+}
+
+int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
+			   struct packet_type *ptype, struct net_device *orig_dev)
+{
+	struct sk_buff *nskb;
+	struct x25_neigh *nb;
+
+	if (!net_eq(dev_net(dev), &init_net))
+		goto drop;
+
+	nskb = skb_copy(skb, GFP_ATOMIC);
+	if (!nskb)
+		goto drop;
+	kfree_skb(skb);
+	skb = nskb;
+
+	/*
+	 * Packet received from unrecognised device, throw it away.
+	 */
+	nb = x25_get_neigh(dev);
+	if (!nb) {
+		pr_debug("unknown neighbour - %s\n", dev->name);
+		goto drop;
+	}
+
+	if (!pskb_may_pull(skb, 1)) {
+		x25_neigh_put(nb);
+		goto drop;
+	}
+
+	switch (skb->data[0]) {
+
+	case X25_IFACE_DATA:
+		skb_pull(skb, 1);
+		if (x25_receive_data(skb, nb)) {
+			x25_neigh_put(nb);
+			goto out;
+		}
+		break;
+
+	case X25_IFACE_CONNECT:
+		x25_link_established(nb);
+		break;
+
+	case X25_IFACE_DISCONNECT:
+		x25_link_terminated(nb);
+		break;
+	}
+	x25_neigh_put(nb);
+drop:
+	kfree_skb(skb);
+out:
+	return 0;
+}
+
+void x25_establish_link(struct x25_neigh *nb)
+{
+	struct sk_buff *skb;
+	unsigned char *ptr;
+
+	switch (nb->dev->type) {
+	case ARPHRD_X25:
+		if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
+			pr_err("x25_dev: out of memory\n");
+			return;
+		}
+		ptr  = skb_put(skb, 1);
+		*ptr = X25_IFACE_CONNECT;
+		break;
+
+	default:
+		return;
+	}
+
+	skb->protocol = htons(ETH_P_X25);
+	skb->dev      = nb->dev;
+
+	dev_queue_xmit(skb);
+}
+
+void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
+{
+	unsigned char *dptr;
+
+	skb_reset_network_header(skb);
+
+	switch (nb->dev->type) {
+	case ARPHRD_X25:
+		dptr  = skb_push(skb, 1);
+		*dptr = X25_IFACE_DATA;
+		break;
+
+	default:
+		kfree_skb(skb);
+		return;
+	}
+
+	skb->protocol = htons(ETH_P_X25);
+	skb->dev      = nb->dev;
+
+	dev_queue_xmit(skb);
+}