USB: fix possible deadlock involving sysfs attributes (e16362a0) · Commits · 戴 / test

There is a potential deadlock when the usb_generic driver is unbound from a device. The problem is that generic_disconnect() is called with the device lock held, and it removes a bunch of device attributes from sysfs. If a user task happens to be running an attribute method at the time, the removal will block until the method returns. But at least one of the attribute methods (the store routine for power/level) needs to acquire the device lock! This patch (as1093) eliminates the deadlock by moving the calls to create and remove the sysfs attributes from the usb_generic driver into usb_new_device() and usb_disconnect(), where they can be invoked without holding the device lock. Besides, the other sysfs attributes are created when the device is registered and removed when the device is unregistered. So it seems only fitting for the extra attributes to be created and removed at the same time. Signed-off-by:

Alan Stern <stern@rowland.harvard.edu> Signed-off-by:

Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/generic.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -155,9 +155,6 @@ static int generic_probe(struct usb_device *udev)
		{
		int err, c;

		/* put device-specific files into sysfs */
		usb_create_sysfs_dev_files(udev);

		/* Choose and set the configuration. This registers the interfaces
		* with the driver core and lets interface drivers bind to them.
		*/
		@@ -189,8 +186,6 @@ static void generic_disconnect(struct usb_device *udev)
		* unconfigure the device */
		if (udev->actconfig)
		usb_set_configuration(udev, -1);

		usb_remove_sysfs_dev_files(udev);
		}

		#ifdef CONFIG_PM

drivers/usb/core/hub.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -1326,6 +1326,12 @@ void usb_disconnect(struct usb_device **pdev)

		usb_unlock_device(udev);

		/* Remove the device-specific files from sysfs. This must be
		* done with udev unlocked, because some of the attribute
		* routines try to acquire the device lock.
		*/
		usb_remove_sysfs_dev_files(udev);

		/* Unregister the device. The device driver is responsible
		* for removing the device files from usbfs and sysfs and for
		* de-configuring the device.
		@@ -1541,6 +1547,9 @@ int usb_new_device(struct usb_device *udev)
		goto fail;
		}

		/* put device-specific files into sysfs */
		usb_create_sysfs_dev_files(udev);

		/* Tell the world! */
		announce_device(udev);
		return err;

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