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, 105 insertions, 0 deletions

diff --git a/net/bluetooth/hci_drv.c b/net/bluetooth/hci_drv.c
new file mode 100644
index 000000000..3dd2d8a00
--- /dev/null
+++ b/net/bluetooth/hci_drv.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Google Corporation
+ */
+
+#include <linux/skbuff.h>
+#include <linux/types.h>
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci.h>
+#include <net/bluetooth/hci_core.h>
+#include <net/bluetooth/hci_drv.h>
+
+int hci_drv_cmd_status(struct hci_dev *hdev, u16 cmd, u8 status)
+{
+	struct hci_drv_ev_hdr *hdr;
+	struct hci_drv_ev_cmd_status *ev;
+	struct sk_buff *skb;
+
+	skb = bt_skb_alloc(sizeof(*hdr) + sizeof(*ev), GFP_KERNEL);
+	if (!skb)
+		return -ENOMEM;
+
+	hdr = skb_put(skb, sizeof(*hdr));
+	hdr->opcode = __cpu_to_le16(HCI_DRV_EV_CMD_STATUS);
+	hdr->len = __cpu_to_le16(sizeof(*ev));
+
+	ev = skb_put(skb, sizeof(*ev));
+	ev->opcode = __cpu_to_le16(cmd);
+	ev->status = status;
+
+	hci_skb_pkt_type(skb) = HCI_DRV_PKT;
+
+	return hci_recv_frame(hdev, skb);
+}
+EXPORT_SYMBOL(hci_drv_cmd_status);
+
+int hci_drv_cmd_complete(struct hci_dev *hdev, u16 cmd, u8 status, void *rp,
+			 size_t rp_len)
+{
+	struct hci_drv_ev_hdr *hdr;
+	struct hci_drv_ev_cmd_complete *ev;
+	struct sk_buff *skb;
+
+	skb = bt_skb_alloc(sizeof(*hdr) + sizeof(*ev) + rp_len, GFP_KERNEL);
+	if (!skb)
+		return -ENOMEM;
+
+	hdr = skb_put(skb, sizeof(*hdr));
+	hdr->opcode = __cpu_to_le16(HCI_DRV_EV_CMD_COMPLETE);
+	hdr->len = __cpu_to_le16(sizeof(*ev) + rp_len);
+
+	ev = skb_put(skb, sizeof(*ev));
+	ev->opcode = __cpu_to_le16(cmd);
+	ev->status = status;
+
+	skb_put_data(skb, rp, rp_len);
+
+	hci_skb_pkt_type(skb) = HCI_DRV_PKT;
+
+	return hci_recv_frame(hdev, skb);
+}
+EXPORT_SYMBOL(hci_drv_cmd_complete);
+
+int hci_drv_process_cmd(struct hci_dev *hdev, struct sk_buff *skb)
+{
+	struct hci_drv_cmd_hdr *hdr;
+	const struct hci_drv_handler *handler = NULL;
+	u16 opcode, len, ogf, ocf;
+
+	hdr = skb_pull_data(skb, sizeof(*hdr));
+	if (!hdr)
+		return -EILSEQ;
+
+	opcode = __le16_to_cpu(hdr->opcode);
+	len = __le16_to_cpu(hdr->len);
+	if (len != skb->len)
+		return -EILSEQ;
+
+	ogf = hci_opcode_ogf(opcode);
+	ocf = hci_opcode_ocf(opcode);
+
+	if (!hdev->hci_drv)
+		return hci_drv_cmd_status(hdev, opcode,
+					  HCI_DRV_STATUS_UNKNOWN_COMMAND);
+
+	if (ogf != HCI_DRV_OGF_DRIVER_SPECIFIC) {
+		if (opcode < hdev->hci_drv->common_handler_count)
+			handler = &hdev->hci_drv->common_handlers[opcode];
+	} else {
+		if (ocf < hdev->hci_drv->specific_handler_count)
+			handler = &hdev->hci_drv->specific_handlers[ocf];
+	}
+
+	if (!handler || !handler->func)
+		return hci_drv_cmd_status(hdev, opcode,
+					  HCI_DRV_STATUS_UNKNOWN_COMMAND);
+
+	if (len != handler->data_len)
+		return hci_drv_cmd_status(hdev, opcode,
+					  HCI_DRV_STATUS_INVALID_PARAMETERS);
+
+	return handler->func(hdev, skb->data, len);
+}
+EXPORT_SYMBOL(hci_drv_process_cmd);