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

Ever since commit 83e83ecb79 ("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>
This commit is contained in:
Alan Stern 2023-01-31 15:49:04 -05:00 committed by Greg Kroah-Hartman
parent 49814e2c9c
commit 45bf39f8df
2 changed files with 2 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/usb/core/hub.c
View File

@ -2389,9 +2389,8 @@ static int usb_enumerate_device_otg(struct usb_device *udev)
* 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

5
drivers/usb/core/sysfs.c
View File

@ -869,11 +869,7 @@ read_descriptors(struct file *filp, struct kobject *kobj,
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, struct kobject *kobj,
off -= srclen;
}
}
usb_unlock_device(udev);
return count - nleft;
}