Bluetooth: vhci: Prevent use-after-free by removing debugfs files early

Move the creation of debugfs files into a dedicated function, and ensure
they are explicitly removed during vhci_release(), before associated
data structures are freed.

Previously, debugfs files such as "force_suspend", "force_wakeup", and
others were created under hdev->debugfs but not removed in
vhci_release(). Since vhci_release() frees the backing vhci_data
structure, any access to these files after release would result in
use-after-free errors.

Although hdev->debugfs is later freed in hci_release_dev(), user can
access files after vhci_data is freed but before hdev->debugfs is
released.

Fixes: ab4e4380d4e1 ("Bluetooth: Add vhci devcoredump support")
Signed-off-by: Ivan Pravdin <[e-mail]>
Reviewed-by: Paul Menzel <[e-mail]>
Signed-off-by: Luiz Augusto von Dentz <[e-mail]>

drivers/bluetooth/hci_vhci.c

···
 	.write		= force_devcd_write,
 };
 
+static void vhci_debugfs_init(struct vhci_data *data)
+{
+	struct hci_dev *hdev = data->hdev;
+
+	debugfs_create_file("force_suspend", 0644, hdev->debugfs, data,
+			    &force_suspend_fops);
+
+	debugfs_create_file("force_wakeup", 0644, hdev->debugfs, data,
+			    &force_wakeup_fops);
+
+	if (IS_ENABLED(CONFIG_BT_MSFTEXT))
+		debugfs_create_file("msft_opcode", 0644, hdev->debugfs, data,
+				    &msft_opcode_fops);
+
+	if (IS_ENABLED(CONFIG_BT_AOSPEXT))
+		debugfs_create_file("aosp_capable", 0644, hdev->debugfs, data,
+				    &aosp_capable_fops);
+
+	debugfs_create_file("force_devcoredump", 0644, hdev->debugfs, data,
+			    &force_devcoredump_fops);
+}
+
 static int __vhci_create_device(struct vhci_data *data, __u8 opcode)
 {
 	struct hci_dev *hdev;
···
 		return -EBUSY;
 	}
 
-	debugfs_create_file("force_suspend", 0644, hdev->debugfs, data,
-			    &force_suspend_fops);
-
-	debugfs_create_file("force_wakeup", 0644, hdev->debugfs, data,
-			    &force_wakeup_fops);
-
-	if (IS_ENABLED(CONFIG_BT_MSFTEXT))
-		debugfs_create_file("msft_opcode", 0644, hdev->debugfs, data,
-				    &msft_opcode_fops);
-
-	if (IS_ENABLED(CONFIG_BT_AOSPEXT))
-		debugfs_create_file("aosp_capable", 0644, hdev->debugfs, data,
-				    &aosp_capable_fops);
-
-	debugfs_create_file("force_devcoredump", 0644, hdev->debugfs, data,
-			    &force_devcoredump_fops);
+	if (!IS_ERR_OR_NULL(hdev->debugfs))
+		vhci_debugfs_init(data);
 
 	hci_skb_pkt_type(skb) = HCI_VENDOR_PKT;
 
···
 	return 0;
 }
 
+static void vhci_debugfs_remove(struct hci_dev *hdev)
+{
+	debugfs_lookup_and_remove("force_suspend", hdev->debugfs);
+
+	debugfs_lookup_and_remove("force_wakeup", hdev->debugfs);
+
+	if (IS_ENABLED(CONFIG_BT_MSFTEXT))
+		debugfs_lookup_and_remove("msft_opcode", hdev->debugfs);
+
+	if (IS_ENABLED(CONFIG_BT_AOSPEXT))
+		debugfs_lookup_and_remove("aosp_capable", hdev->debugfs);
+
+	debugfs_lookup_and_remove("force_devcoredump", hdev->debugfs);
+}
+
 static int vhci_release(struct inode *inode, struct file *file)
 {
 	struct vhci_data *data = file->private_data;
···
 	hdev = data->hdev;
 
 	if (hdev) {
+		if (!IS_ERR_OR_NULL(hdev->debugfs))
+			vhci_debugfs_remove(hdev);
 		hci_unregister_dev(hdev);
 		hci_free_dev(hdev);
 	}