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, 120 insertions, 0 deletions

diff --git a/net/llc/llc_station.c b/net/llc/llc_station.c
new file mode 100644
index 000000000..77fd0ac75
--- /dev/null
+++ b/net/llc/llc_station.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * llc_station.c - station component of LLC
+ *
+ * Copyright (c) 1997 by Procom Technology, Inc.
+ * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <net/llc.h>
+#include <net/llc_sap.h>
+#include <net/llc_conn.h>
+#include <net/llc_c_ac.h>
+#include <net/llc_s_ac.h>
+#include <net/llc_c_ev.h>
+#include <net/llc_c_st.h>
+#include <net/llc_s_ev.h>
+#include <net/llc_s_st.h>
+#include <net/llc_pdu.h>
+
+static int llc_stat_ev_rx_null_dsap_xid_c(struct sk_buff *skb)
+{
+	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
+
+	return LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
+	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
+	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_XID &&
+	       !pdu->dsap;				/* NULL DSAP value */
+}
+
+static int llc_stat_ev_rx_null_dsap_test_c(struct sk_buff *skb)
+{
+	struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
+
+	return LLC_PDU_IS_CMD(pdu) &&			/* command PDU */
+	       LLC_PDU_TYPE_IS_U(pdu) &&		/* U type PDU */
+	       LLC_U_PDU_CMD(pdu) == LLC_1_PDU_CMD_TEST &&
+	       !pdu->dsap;				/* NULL DSAP */
+}
+
+static int llc_station_ac_send_xid_r(struct sk_buff *skb)
+{
+	u8 mac_da[ETH_ALEN], dsap;
+	int rc = 1;
+	struct sk_buff *nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U,
+					       sizeof(struct llc_xid_info));
+
+	if (!nskb)
+		goto out;
+	llc_pdu_decode_sa(skb, mac_da);
+	llc_pdu_decode_ssap(skb, &dsap);
+	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
+	llc_pdu_init_as_xid_rsp(nskb, LLC_XID_NULL_CLASS_2, 127);
+	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
+	if (unlikely(rc))
+		goto free;
+	dev_queue_xmit(nskb);
+out:
+	return rc;
+free:
+	kfree_skb(nskb);
+	goto out;
+}
+
+static int llc_station_ac_send_test_r(struct sk_buff *skb)
+{
+	u8 mac_da[ETH_ALEN], dsap;
+	int rc = 1;
+	u32 data_size;
+	struct sk_buff *nskb;
+
+	if (skb->mac_len < ETH_HLEN)
+		goto out;
+
+	/* The test request command is type U (llc_len = 3) */
+	data_size = ntohs(eth_hdr(skb)->h_proto) - 3;
+	nskb = llc_alloc_frame(NULL, skb->dev, LLC_PDU_TYPE_U, data_size);
+
+	if (!nskb)
+		goto out;
+	llc_pdu_decode_sa(skb, mac_da);
+	llc_pdu_decode_ssap(skb, &dsap);
+	llc_pdu_header_init(nskb, LLC_PDU_TYPE_U, 0, dsap, LLC_PDU_RSP);
+	llc_pdu_init_as_test_rsp(nskb, skb);
+	rc = llc_mac_hdr_init(nskb, skb->dev->dev_addr, mac_da);
+	if (unlikely(rc))
+		goto free;
+	dev_queue_xmit(nskb);
+out:
+	return rc;
+free:
+	kfree_skb(nskb);
+	goto out;
+}
+
+/**
+ *	llc_station_rcv - send received pdu to the station state machine
+ *	@skb: received frame.
+ *
+ *	Sends data unit to station state machine.
+ */
+static void llc_station_rcv(struct sk_buff *skb)
+{
+	if (llc_stat_ev_rx_null_dsap_xid_c(skb))
+		llc_station_ac_send_xid_r(skb);
+	else if (llc_stat_ev_rx_null_dsap_test_c(skb))
+		llc_station_ac_send_test_r(skb);
+	kfree_skb(skb);
+}
+
+void __init llc_station_init(void)
+{
+	llc_set_station_handler(llc_station_rcv);
+}
+
+void llc_station_exit(void)
+{
+	llc_set_station_handler(NULL);
+}