linux-kernel - [PATCH v3 2/2] usb: core: Make default authorization mode configurable

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Date: Fri,  9 Feb 2024 11:46:51 +0200
From: niko.mauno@...sala.com
To: gregkh@...uxfoundation.org
Cc: linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	vesa.jaaskelainen@...sala.com,
	geert@...ux-m68k.org,
	Niko Mauno <niko.mauno@...sala.com>
Subject: [PATCH v3 2/2] usb: core: Make default authorization mode configurable

From: Niko Mauno <niko.mauno@...sala.com>

Make the default USB device authorization mode configurable at build
time. This is useful for systems that require a mode that is stricter
than the standard setting, as it avoids relying on the kernel command
line being properly set.

Signed-off-by: Niko Mauno <niko.mauno@...sala.com>
---
 drivers/usb/core/Kconfig | 28 ++++++++++++++++++++++++++++
 drivers/usb/core/hcd.c   |  2 +-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index 351ede4b5de2..0bf425889c10 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -116,3 +116,31 @@ config USB_AUTOSUSPEND_DELAY
 	  The default value Linux has always had is 2 seconds.  Change
 	  this value if you want a different delay and cannot modify
 	  the command line or module parameter.
+
+config USB_DEFAULT_AUTHORIZATION_MODE
+	int "Default authorization mode for USB devices"
+	range 0 2
+	default 1
+	depends on USB
+	help
+	  Select the default USB device authorization mode. Can be overridden
+	  with usbcore.authorized_default command line or module parameter.
+
+	  This option allows you to choose whether USB devices that are
+	  connected to the system can be used by default, or if they are
+	  locked down.
+
+	  With value 0 all connected USB devices with the exception of root
+	  hub require user space authorization before they can be used.
+
+	  With value 1 (default) no user space authorization is required to
+	  use connected USB devices.
+
+	  With value 2 all connected USB devices with exception of internal
+	  USB devices require user space authorization before they can be
+	  used. Note that in this mode the differentiation between internal
+	  and external USB devices relies on ACPI, and on systems without
+	  ACPI selecting value 2 is analogous to selecting value 0.
+
+	  If the default value is too permissive but you are unsure which
+	  mode to use, say 2.
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 9aa5e6bf9b9d..d56597dc7d42 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -357,7 +357,7 @@ static const u8 ss_rh_config_descriptor[] = {
 #define USB_AUTHORIZE_ALL	1
 #define USB_AUTHORIZE_INTERNAL	2
 
-static int authorized_default = USB_AUTHORIZE_ALL;
+static int authorized_default = CONFIG_USB_DEFAULT_AUTHORIZATION_MODE;
 module_param(authorized_default, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(authorized_default,
 		"Default USB device authorization: 0 is not authorized, 1 is authorized (default), 2 is authorized for internal devices, -1 is authorized (same as 1)");
-- 
2.39.2