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USB: usb-skeleton.c: fix open/disconnect race

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If usb device is disconnected between usb_get_intfdata()
and kref_get() in skel_open(), kref_get may access a freed
object.

Also check if device is disconnected in ->open.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Ming Lei 2011-12-16 22:20:01 +08:00 committed by Greg Kroah-Hartman
parent e78832cdca
commit 26c71a79ca
1 changed files with 17 additions and 1 deletions
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18
drivers/usb/usb-skeleton.c
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@ -27,6 +27,8 @@
#define USB_SKEL_VENDOR_ID 0xfff0
#define USB_SKEL_PRODUCT_ID 0xfff0
static DEFINE_MUTEX(skel_mutex);
/* table of devices that work with this driver */
static const struct usb_device_id skel_table[] = {
{ USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
@ -100,18 +102,25 @@ static int skel_open(struct inode *inode, struct file *file)
goto exit;
}
mutex_lock(&skel_mutex);
dev = usb_get_intfdata(interface);
if (!dev) {
mutex_unlock(&skel_mutex);
retval = -ENODEV;
goto exit;
}
/* increment our usage count for the device */
kref_get(&dev->kref);
mutex_unlock(&skel_mutex);
/* lock the device to allow correctly handling errors
* in resumption */
mutex_lock(&dev->io_mutex);
if (!dev->interface) {
retval = -ENODEV;
goto out_err;
}
if (!dev->open_count++) {
retval = usb_autopm_get_interface(interface);
@ -132,7 +141,11 @@ static int skel_open(struct inode *inode, struct file *file)
/* save our object in the file's private structure */
file->private_data = dev;
out_err:
mutex_unlock(&dev->io_mutex);
if (retval)
kref_put(&dev->kref, skel_delete);
exit:
return retval;
@ -612,7 +625,6 @@ static void skel_disconnect(struct usb_interface *interface)
int minor = interface->minor;
dev = usb_get_intfdata(interface);
usb_set_intfdata(interface, NULL);
/* give back our minor */
usb_deregister_dev(interface, &skel_class);
@ -624,8 +636,12 @@ static void skel_disconnect(struct usb_interface *interface)
usb_kill_anchored_urbs(&dev->submitted);
mutex_lock(&skel_mutex);
usb_set_intfdata(interface, NULL);
/* decrement our usage count */
kref_put(&dev->kref, skel_delete);
mutex_unlock(&skel_mutex);
dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
}