patch "USB: Fix device driver race" added to usb-linus

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    USB: Fix device driver race

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


From d5643d2249b279077427b2c2b2ffae9b70c95b0b Mon Sep 17 00:00:00 2001
From: Bastien Nocera <hadess@hadess.net>
Date: Tue, 18 Aug 2020 13:04:45 +0200
Subject: USB: Fix device driver race

When a new device with a specialised device driver is plugged in, the
new driver will be modprobe()'d but the driver core will attach the
"generic" driver to the device.

After that, nothing will trigger a reprobe when the modprobe()'d device
driver has finished initialising, as the device has the "generic"
driver attached to it.

Trigger a reprobe ourselves when new specialised drivers get registered.

Fixes: 88b7381a939d ("USB: Select better matching USB drivers when available")
Signed-off-by: Bastien Nocera <hadess@hadess.net>
Cc: stable <stable@vger.kernel.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20200818110445.509668-3-hadess@hadess.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/core/driver.c | 40 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index f81606c6a35b..7e73e989645b 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -905,6 +905,35 @@ static int usb_uevent(struct device *dev, struct kobj_uevent_env *env)
 	return 0;
 }
 
+static bool is_dev_usb_generic_driver(struct device *dev)
+{
+	struct usb_device_driver *udd = dev->driver ?
+		to_usb_device_driver(dev->driver) : NULL;
+
+	return udd == &usb_generic_driver;
+}
+
+static int __usb_bus_reprobe_drivers(struct device *dev, void *data)
+{
+	struct usb_device_driver *new_udriver = data;
+	struct usb_device *udev;
+	int ret;
+
+	if (!is_dev_usb_generic_driver(dev))
+		return 0;
+
+	udev = to_usb_device(dev);
+	if (usb_device_match_id(udev, new_udriver->id_table) == NULL &&
+	    (!new_udriver->match || new_udriver->match(udev) != 0))
+		return 0;
+
+	ret = device_reprobe(dev);
+	if (ret && ret != -EPROBE_DEFER)
+		dev_err(dev, "Failed to reprobe device (error %d)\n", ret);
+
+	return 0;
+}
+
 /**
  * usb_register_device_driver - register a USB device (not interface) driver
  * @new_udriver: USB operations for the device driver
@@ -934,13 +963,20 @@ int usb_register_device_driver(struct usb_device_driver *new_udriver,
 
 	retval = driver_register(&new_udriver->drvwrap.driver);
 
-	if (!retval)
+	if (!retval) {
 		pr_info("%s: registered new device driver %s\n",
 			usbcore_name, new_udriver->name);
-	else
+		/*
+		 * Check whether any device could be better served with
+		 * this new driver
+		 */
+		bus_for_each_dev(&usb_bus_type, NULL, new_udriver,
+				 __usb_bus_reprobe_drivers);
+	} else {
 		printk(KERN_ERR "%s: error %d registering device "
 			"	driver %s\n",
 			usbcore_name, retval, new_udriver->name);
+	}
 
 	return retval;
 }
-- 
2.28.0