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, 274 insertions, 0 deletions

diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
new file mode 100644
index 000000000..767372707
--- /dev/null
+++ b/drivers/bluetooth/hci_h4.c
@@ -0,0 +1,274 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ *  Bluetooth HCI UART driver
+ *
+ *  Copyright (C) 2000-2001  Qualcomm Incorporated
+ *  Copyright (C) 2002-2003  Maxim Krasnyansky <maxk@qualcomm.com>
+ *  Copyright (C) 2004-2005  Marcel Holtmann <marcel@holtmann.org>
+ */
+
+#include <linux/module.h>
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/fcntl.h>
+#include <linux/interrupt.h>
+#include <linux/ptrace.h>
+#include <linux/poll.h>
+
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/signal.h>
+#include <linux/ioctl.h>
+#include <linux/skbuff.h>
+#include <linux/unaligned.h>
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+
+#include "hci_uart.h"
+
+struct h4_struct {
+	struct sk_buff *rx_skb;
+	struct sk_buff_head txq;
+};
+
+/* Initialize protocol */
+static int h4_open(struct hci_uart *hu)
+{
+	struct h4_struct *h4;
+
+	BT_DBG("hu %p", hu);
+
+	h4 = kzalloc_obj(*h4);
+	if (!h4)
+		return -ENOMEM;
+
+	skb_queue_head_init(&h4->txq);
+
+	hu->priv = h4;
+	return 0;
+}
+
+/* Flush protocol data */
+static int h4_flush(struct hci_uart *hu)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	BT_DBG("hu %p", hu);
+
+	skb_queue_purge(&h4->txq);
+
+	return 0;
+}
+
+/* Close protocol */
+static int h4_close(struct hci_uart *hu)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	BT_DBG("hu %p", hu);
+
+	skb_queue_purge(&h4->txq);
+
+	kfree_skb(h4->rx_skb);
+
+	hu->priv = NULL;
+	kfree(h4);
+
+	return 0;
+}
+
+/* Enqueue frame for transmission (padding, crc, etc) */
+static int h4_enqueue(struct hci_uart *hu, struct sk_buff *skb)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	BT_DBG("hu %p skb %p", hu, skb);
+
+	/* Prepend skb with frame type */
+	memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1);
+	skb_queue_tail(&h4->txq, skb);
+
+	return 0;
+}
+
+static const struct h4_recv_pkt h4_recv_pkts[] = {
+	{ H4_RECV_ACL,   .recv = hci_recv_frame },
+	{ H4_RECV_SCO,   .recv = hci_recv_frame },
+	{ H4_RECV_EVENT, .recv = hci_recv_frame },
+	{ H4_RECV_ISO,   .recv = hci_recv_frame },
+};
+
+/* Recv data */
+static int h4_recv(struct hci_uart *hu, const void *data, int count)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	if (!h4)
+		return -ENODEV;
+
+	h4->rx_skb = h4_recv_buf(hu, h4->rx_skb, data, count,
+				 h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
+	if (IS_ERR(h4->rx_skb)) {
+		int err = PTR_ERR(h4->rx_skb);
+		bt_dev_err(hu->hdev, "Frame reassembly failed (%d)", err);
+		h4->rx_skb = NULL;
+		return err;
+	}
+
+	return count;
+}
+
+static struct sk_buff *h4_dequeue(struct hci_uart *hu)
+{
+	struct h4_struct *h4 = hu->priv;
+	return skb_dequeue(&h4->txq);
+}
+
+static const struct hci_uart_proto h4p = {
+	.id		= HCI_UART_H4,
+	.name		= "H4",
+	.open		= h4_open,
+	.close		= h4_close,
+	.recv		= h4_recv,
+	.enqueue	= h4_enqueue,
+	.dequeue	= h4_dequeue,
+	.flush		= h4_flush,
+};
+
+int __init h4_init(void)
+{
+	return hci_uart_register_proto(&h4p);
+}
+
+int __exit h4_deinit(void)
+{
+	return hci_uart_unregister_proto(&h4p);
+}
+
+struct sk_buff *h4_recv_buf(struct hci_uart *hu, struct sk_buff *skb,
+			    const unsigned char *buffer, int count,
+			    const struct h4_recv_pkt *pkts, int pkts_count)
+{
+	u8 alignment = hu->alignment ? hu->alignment : 1;
+	struct hci_dev *hdev = hu->hdev;
+
+	/* Check for error from previous call */
+	if (IS_ERR(skb))
+		skb = NULL;
+
+	while (count) {
+		int i, len;
+
+		/* remove padding bytes from buffer */
+		for (; hu->padding && count > 0; hu->padding--) {
+			count--;
+			buffer++;
+		}
+		if (!count)
+			break;
+
+		if (!skb) {
+			for (i = 0; i < pkts_count; i++) {
+				if (buffer[0] != (&pkts[i])->type)
+					continue;
+
+				skb = bt_skb_alloc((&pkts[i])->maxlen,
+						   GFP_ATOMIC);
+				if (!skb)
+					return ERR_PTR(-ENOMEM);
+
+				hci_skb_pkt_type(skb) = (&pkts[i])->type;
+				hci_skb_expect(skb) = (&pkts[i])->hlen;
+				break;
+			}
+
+			/* Check for invalid packet type */
+			if (!skb)
+				return ERR_PTR(-EILSEQ);
+
+			count -= 1;
+			buffer += 1;
+		}
+
+		len = min_t(uint, hci_skb_expect(skb) - skb->len, count);
+		skb_put_data(skb, buffer, len);
+
+		count -= len;
+		buffer += len;
+
+		/* Check for partial packet */
+		if (skb->len < hci_skb_expect(skb))
+			continue;
+
+		for (i = 0; i < pkts_count; i++) {
+			if (hci_skb_pkt_type(skb) == (&pkts[i])->type)
+				break;
+		}
+
+		if (i >= pkts_count) {
+			kfree_skb(skb);
+			return ERR_PTR(-EILSEQ);
+		}
+
+		if (skb->len == (&pkts[i])->hlen) {
+			u16 dlen;
+
+			switch ((&pkts[i])->lsize) {
+			case 0:
+				/* No variable data length */
+				dlen = 0;
+				break;
+			case 1:
+				/* Single octet variable length */
+				dlen = skb->data[(&pkts[i])->loff];
+				hci_skb_expect(skb) += dlen;
+
+				if (skb_tailroom(skb) < dlen) {
+					kfree_skb(skb);
+					return ERR_PTR(-EMSGSIZE);
+				}
+				break;
+			case 2:
+				/* Double octet variable length */
+				dlen = get_unaligned_le16(skb->data +
+							  (&pkts[i])->loff);
+				hci_skb_expect(skb) += dlen;
+
+				if (skb_tailroom(skb) < dlen) {
+					kfree_skb(skb);
+					return ERR_PTR(-EMSGSIZE);
+				}
+				break;
+			default:
+				/* Unsupported variable length */
+				kfree_skb(skb);
+				return ERR_PTR(-EILSEQ);
+			}
+
+			if (!dlen) {
+				hu->padding = (skb->len + 1) % alignment;
+				hu->padding = (alignment - hu->padding) % alignment;
+
+				/* No more data, complete frame */
+				(&pkts[i])->recv(hdev, skb);
+				skb = NULL;
+			}
+		} else {
+			hu->padding = (skb->len + 1) % alignment;
+			hu->padding = (alignment - hu->padding) % alignment;
+
+			/* Complete frame */
+			(&pkts[i])->recv(hdev, skb);
+			skb = NULL;
+		}
+	}
+
+	return skb;
+}
+EXPORT_SYMBOL_GPL(h4_recv_buf);