From: Alan Stern stern@rowland.harvard.edu
commit 45bf39f8df7f05efb83b302c65ae3b9bc92b7065 upstream.
Ever since commit 83e83ecb79a8 ("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 --- drivers/usb/core/hub.c | 5 ++--- drivers/usb/core/sysfs.c | 5 ----- 2 files changed, 2 insertions(+), 8 deletions(-)
--- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -2322,9 +2322,8 @@ static int usb_enumerate_device_otg(stru * usb_enumerate_device - Read device configs/intfs/otg (usbcore-internal) * @udev: newly addressed device (in ADDRESS state) * - * This is only called by usb_new_device() and usb_authorize_device() - * and FIXME -- all comments that apply to them apply here wrt to - * environment. + * This is only called by usb_new_device() -- all comments that apply there + * apply here wrt to environment. * * If the device is WUSB and not authorized, we don't attempt to read * the string descriptors, as they will be errored out by the device --- a/drivers/usb/core/sysfs.c +++ b/drivers/usb/core/sysfs.c @@ -865,11 +865,7 @@ read_descriptors(struct file *filp, stru size_t srclen, n; int cfgno; void *src; - int retval;
- retval = usb_lock_device_interruptible(udev); - if (retval < 0) - return -EINTR; /* The binary attribute begins with the device descriptor. * Following that are the raw descriptor entries for all the * configurations (config plus subsidiary descriptors). @@ -894,7 +890,6 @@ read_descriptors(struct file *filp, stru off -= srclen; } } - usb_unlock_device(udev); return count - nleft; }