USB: core: Don't hold device lock while reading the "descriptors" sysfs file

stable inclusion
from stable-v5.10.171
commit 218925bfd5d1436e337c4f961e9c149fbe32de6d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7V9QX

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=218925bfd5d1436e337c4f961e9c149fbe32de6d



----------------------------------------------------

commit 45bf39f8 upstream.

Ever since commit 83e83ecb ("usb: core: get config and string
descriptors for unauthorized devices") was merged in 2013, there has
been no mechanism for reallocating the rawdescriptors buffers in
struct usb_device after the initial enumeration.  Before that commit,
the buffers would be deallocated when a device was deauthorized and
reallocated when it was authorized and enumerated.

This means that the locking in the read_descriptors() routine is not
needed, since the buffers it reads will never be reallocated while the
routine is running.  This locking can interfere with user programs
trying to read a hub's descriptors via sysfs while new child devices
of the hub are being initialized, since the hub is locked during this
procedure.

Since the locking in read_descriptors() hasn't been needed for over
nine years, we can remove it.

Reported-and-tested-by: Troels Liebe Bentsen <troels@connectedcars.dk>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: stable@vger.kernel.org
Link: https://lore.kernel.org/r/Y9l+wDTRbuZABzsE@rowland.harvard.edu


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>