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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>