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, 74 insertions, 0 deletions

diff --git a/net/llc/llc_output.c b/net/llc/llc_output.c
new file mode 100644
index 000000000..5a6466fc6
--- /dev/null
+++ b/net/llc/llc_output.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * llc_output.c - LLC minimal output path
+ *
+ * Copyright (c) 1997 by Procom Technology, Inc.
+ * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ */
+
+#include <linux/if_arp.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/export.h>
+#include <net/llc.h>
+#include <net/llc_pdu.h>
+
+/**
+ *	llc_mac_hdr_init - fills MAC header fields
+ *	@skb: Address of the frame to initialize its MAC header
+ *	@sa: The MAC source address
+ *	@da: The MAC destination address
+ *
+ *	Fills MAC header fields, depending on MAC type. Returns 0, If MAC type
+ *	is a valid type and initialization completes correctly 1, otherwise.
+ */
+int llc_mac_hdr_init(struct sk_buff *skb,
+		     const unsigned char *sa, const unsigned char *da)
+{
+	int rc = -EINVAL;
+
+	switch (skb->dev->type) {
+	case ARPHRD_ETHER:
+	case ARPHRD_LOOPBACK:
+		rc = dev_hard_header(skb, skb->dev, ETH_P_802_2, da, sa,
+				     skb->len);
+		if (rc > 0)
+			rc = 0;
+		break;
+	default:
+		break;
+	}
+	return rc;
+}
+
+/**
+ *	llc_build_and_send_ui_pkt - unitdata request interface for upper layers
+ *	@sap: sap to use
+ *	@skb: packet to send
+ *	@dmac: destination mac address
+ *	@dsap: destination sap
+ *
+ *	Upper layers calls this function when upper layer wants to send data
+ *	using connection-less mode communication (UI pdu).
+ *
+ *	Accept data frame from network layer to be sent using connection-
+ *	less mode communication; timeout/retries handled by network layer;
+ *	package primitive as an event and send to SAP event handler
+ */
+int llc_build_and_send_ui_pkt(struct llc_sap *sap, struct sk_buff *skb,
+			      const unsigned char *dmac, unsigned char dsap)
+{
+	int rc;
+	llc_pdu_header_init(skb, LLC_PDU_TYPE_U, sap->laddr.lsap,
+			    dsap, LLC_PDU_CMD);
+	llc_pdu_init_as_ui_cmd(skb);
+	rc = llc_mac_hdr_init(skb, skb->dev->dev_addr, dmac);
+	if (likely(!rc))
+		rc = dev_queue_xmit(skb);
+	else
+		kfree_skb(skb);
+	return rc;
+}
+
+EXPORT_SYMBOL(llc_mac_hdr_init);
+EXPORT_SYMBOL(llc_build_and_send_ui_pkt);