USB: usb-skeleton leaking locks on open

This weekend I was hacking around with a trivial USB driver for talking
to the boot load firmware of a USB Bit Whacker.  It's running the
MicroChip Pic18 boot loader firmware and I'm putting together a flash
program for writing new FW to the thing.

Anyway in my use of the usb-skeleton.c as my starting point I discovered
my test program was getting hung up after attempting to write a buffer.
The application and driver where hung in a way that required me to
reboot to get it to clean up so I could try again.

It turned out the code path through skel_open can grap the driver's
io_mutex lock and forget to release it.

The following patch fixes the problem for me.

Signed-off-by: Mark Gross <mgross@linux.intel.com>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c
index 8de11deb5d1429dffb16febcd1d834623b59d0c5..c815a40e167f33f7427f0c908514e0e93b685b7d 100644 (file)
--- a/drivers/usb/usb-skeleton.c
+++ b/drivers/usb/usb-skeleton.c
@@ -125,6 +125,7 @@ static int skel_open(struct inode *inode, struct file *file)
 
        /* save our object in the file's private structure */
        file->private_data = dev;
+       mutex_unlock(&dev->io_mutex);
 
 exit:
        return retval;