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@xxxxxxxxxxxxxxxx>
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
---
[as1990]
drivers/usb/core/hub.c | 5 ++---
drivers/usb/core/sysfs.c | 5 -----
2 files changed, 2 insertions(+), 8 deletions(-)
Index: usb-devel/drivers/usb/core/sysfs.c
===================================================================
--- usb-devel.orig/drivers/usb/core/sysfs.c
+++ usb-devel/drivers/usb/core/sysfs.c
@@ -869,11 +869,7 @@ 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).
@@ -898,7 +894,6 @@ read_descriptors(struct file *filp, stru
off -= srclen;
}
}
- usb_unlock_device(udev);
return count - nleft;
}
Index: usb-devel/drivers/usb/core/hub.c
===================================================================
--- usb-devel.orig/drivers/usb/core/hub.c
+++ usb-devel/drivers/usb/core/hub.c
@@ -2386,9 +2386,8 @@ 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
