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USB: fix substandard locking for the sysfs files

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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: Alan Stern <stern@rowland.harvard.edu>
CC: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2013-09-24 15:43:39 -04:00 committed by Greg Kroah-Hartman
parent 9a37a50349
commit 232275a089
1 changed files with 26 additions and 27 deletions
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53
drivers/usb/core/sysfs.c
View File

@ -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;
int s;
intf = to_usb_interface(dev);
udev = interface_to_usbdev(intf);
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);