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: Alan Stern <stern@rowland.harvard.edu> CC: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -23,14 +23,16 @@ static ssize_t field##_show(struct device *dev, \
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{ \
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struct usb_device *udev; \
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struct usb_host_config *actconfig; \
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ssize_t rc = 0; \
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\
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udev = to_usb_device(dev); \
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usb_lock_device(udev); \
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actconfig = udev->actconfig; \
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if (actconfig) \
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return sprintf(buf, format_string, \
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rc = sprintf(buf, format_string, \
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actconfig->desc.field); \
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else \
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return 0; \
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usb_unlock_device(udev); \
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return rc; \
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} \
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#define usb_actconfig_attr(field, format_string) \
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@ -45,12 +47,15 @@ static ssize_t bMaxPower_show(struct device *dev,
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{
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struct usb_device *udev;
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struct usb_host_config *actconfig;
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ssize_t rc = 0;
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udev = to_usb_device(dev);
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usb_lock_device(udev);
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actconfig = udev->actconfig;
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if (!actconfig)
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return 0;
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return sprintf(buf, "%dmA\n", usb_get_max_power(udev, actconfig));
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if (actconfig)
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rc = sprintf(buf, "%dmA\n", usb_get_max_power(udev, actconfig));
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usb_unlock_device(udev);
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return rc;
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}
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static DEVICE_ATTR_RO(bMaxPower);
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@ -59,12 +64,15 @@ static ssize_t configuration_show(struct device *dev,
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{
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struct usb_device *udev;
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struct usb_host_config *actconfig;
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ssize_t rc = 0;
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udev = to_usb_device(dev);
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usb_lock_device(udev);
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actconfig = udev->actconfig;
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if ((!actconfig) || (!actconfig->string))
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return 0;
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return sprintf(buf, "%s\n", actconfig->string);
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if (actconfig && actconfig->string)
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rc = sprintf(buf, "%s\n", actconfig->string);
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usb_unlock_device(udev);
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return rc;
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}
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static DEVICE_ATTR_RO(configuration);
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@ -764,6 +772,7 @@ read_descriptors(struct file *filp, struct kobject *kobj,
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* Following that are the raw descriptor entries for all the
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* configurations (config plus subsidiary descriptors).
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*/
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usb_lock_device(udev);
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for (cfgno = -1; cfgno < udev->descriptor.bNumConfigurations &&
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nleft > 0; ++cfgno) {
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if (cfgno < 0) {
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@ -784,6 +793,7 @@ read_descriptors(struct file *filp, struct kobject *kobj,
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off -= srclen;
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}
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}
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usb_unlock_device(udev);
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return count - nleft;
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}
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@ -870,9 +880,7 @@ static ssize_t interface_show(struct device *dev, struct device_attribute *attr,
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char *string;
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intf = to_usb_interface(dev);
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string = intf->cur_altsetting->string;
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barrier(); /* The altsetting might change! */
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string = ACCESS_ONCE(intf->cur_altsetting->string);
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if (!string)
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return 0;
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return sprintf(buf, "%s\n", string);
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@ -888,7 +896,7 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
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intf = to_usb_interface(dev);
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udev = interface_to_usbdev(intf);
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alt = intf->cur_altsetting;
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alt = ACCESS_ONCE(intf->cur_altsetting);
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return sprintf(buf, "usb:v%04Xp%04Xd%04Xdc%02Xdsc%02Xdp%02X"
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"ic%02Xisc%02Xip%02Xin%02X\n",
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@ -909,23 +917,14 @@ static ssize_t supports_autosuspend_show(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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struct usb_interface *intf;
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struct usb_device *udev;
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int ret;
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int s;
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intf = to_usb_interface(dev);
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udev = interface_to_usbdev(intf);
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usb_lock_device(udev);
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device_lock(dev);
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/* Devices will be autosuspended even when an interface isn't claimed */
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if (!intf->dev.driver ||
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to_usb_driver(intf->dev.driver)->supports_autosuspend)
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ret = sprintf(buf, "%u\n", 1);
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else
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ret = sprintf(buf, "%u\n", 0);
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usb_unlock_device(udev);
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s = (!dev->driver || to_usb_driver(dev->driver)->supports_autosuspend);
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device_unlock(dev);
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return ret;
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return sprintf(buf, "%u\n", s);
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}
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static DEVICE_ATTR_RO(supports_autosuspend);
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