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Commit 232275a0 authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
Browse files

USB: fix substandard locking for the sysfs files 



This patch straightens out some locking issues in the USB sysfs
interface:

	Deauthorization will destroy existing configurations.
	Attributes that read from udev->actconfig need to lock the
	device to prevent races.  Likewise for the rawdescriptor
	values.

	Attributes that access an interface's current alternate
	setting should use ACCESS_ONCE() to obtain the cur_altsetting
	pointer, to protect against concurrent altsetting changes.

	The supports_autosuspend() attribute routine accesses values
	from an interface's driver, so it should lock the interface
	(rather than the usb_device) to protect against concurrent
	unbinds.  Once this is done, the routine can be simplified
	considerably.

Scalar values that are stored directly in the usb_device structure are
always available.  They do not require any locking.  The same is true
of the cached interface string descriptor, because it is not
deallocated until the usb_host_interface structure is destroyed.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
CC: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9a37a503

drivers/usb/core/sysfs.c

+26 −27
Original line number Diff line number Diff line
@@ -23,14 +23,16 @@ static ssize_t field##_show(struct device *dev, \ 
{									\

	struct usb_device *udev;					\

	struct usb_host_config *actconfig;				\

	ssize_t rc = 0;							\

									\

	udev = to_usb_device(dev);					\

	usb_lock_device(udev);						\

	actconfig = udev->actconfig;					\

	if (actconfig)							\

		return sprintf(buf, format_string,			\

		rc = sprintf(buf, format_string,			\

				actconfig->desc.field);			\

	else								\

		return 0;						\

	usb_unlock_device(udev);					\

	return rc;							\

}									\



#define usb_actconfig_attr(field, format_string)		\
@@ -45,12 +47,15 @@ static ssize_t bMaxPower_show(struct device *dev, 
{

	struct usb_device *udev;

	struct usb_host_config *actconfig;

	ssize_t rc = 0;



	udev = to_usb_device(dev);

	usb_lock_device(udev);

	actconfig = udev->actconfig;

	if (!actconfig)

		return 0;

	return sprintf(buf, "%dmA\n", usb_get_max_power(udev, actconfig));

	if (actconfig)

		rc = sprintf(buf, "%dmA\n", usb_get_max_power(udev, actconfig));

	usb_unlock_device(udev);

	return rc;

}

static DEVICE_ATTR_RO(bMaxPower);
@@ -59,12 +64,15 @@ static ssize_t configuration_show(struct device *dev, 
{

	struct usb_device *udev;

	struct usb_host_config *actconfig;

	ssize_t rc = 0;



	udev = to_usb_device(dev);

	usb_lock_device(udev);

	actconfig = udev->actconfig;

	if ((!actconfig) || (!actconfig->string))

		return 0;

	return sprintf(buf, "%s\n", actconfig->string);

	if (actconfig && actconfig->string)

		rc = sprintf(buf, "%s\n", actconfig->string);

	usb_unlock_device(udev);

	return rc;

}

static DEVICE_ATTR_RO(configuration);
@@ -764,6 +772,7 @@ read_descriptors(struct file *filp, struct kobject *kobj, 
	 * Following that are the raw descriptor entries for all the

	 * configurations (config plus subsidiary descriptors).

	 */

	usb_lock_device(udev);

	for (cfgno = -1; cfgno < udev->descriptor.bNumConfigurations &&

			nleft > 0; ++cfgno) {

		if (cfgno < 0) {
@@ -784,6 +793,7 @@ read_descriptors(struct file *filp, struct kobject *kobj, 
			off -= srclen;

		}

	}

	usb_unlock_device(udev);

	return count - nleft;

}
@@ -870,9 +880,7 @@ static ssize_t interface_show(struct device *dev, struct device_attribute *attr, 
	char *string;



	intf = to_usb_interface(dev);

	string = intf->cur_altsetting->string;

	barrier();		/* The altsetting might change! */



	string = ACCESS_ONCE(intf->cur_altsetting->string);

	if (!string)

		return 0;

	return sprintf(buf, "%s\n", string);
@@ -888,7 +896,7 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, 


	intf = to_usb_interface(dev);

	udev = interface_to_usbdev(intf);

	alt = intf->cur_altsetting;

	alt = ACCESS_ONCE(intf->cur_altsetting);



	return sprintf(buf, "usb:v%04Xp%04Xd%04Xdc%02Xdsc%02Xdp%02X"

			"ic%02Xisc%02Xip%02Xin%02X\n",
@@ -909,23 +917,14 @@ static ssize_t supports_autosuspend_show(struct device *dev, 
					 struct device_attribute *attr,

					 char *buf)

{

	struct usb_interface *intf;

	struct usb_device *udev;

	int ret;



	intf = to_usb_interface(dev);

	udev = interface_to_usbdev(intf);

	int s;



	usb_lock_device(udev);

	device_lock(dev);

	/* Devices will be autosuspended even when an interface isn't claimed */

	if (!intf->dev.driver ||

			to_usb_driver(intf->dev.driver)->supports_autosuspend)

		ret = sprintf(buf, "%u\n", 1);

	else

		ret = sprintf(buf, "%u\n", 0);

	usb_unlock_device(udev);

	s = (!dev->driver || to_usb_driver(dev->driver)->supports_autosuspend);

	device_unlock(dev);



	return ret;

	return sprintf(buf, "%u\n", s);

}

static DEVICE_ATTR_RO(supports_autosuspend);