usbhid: prevent deadlock during timeout

On some HCDs usb_unlink_urb() can directly call the
completion handler. That limits the spinlocks that can
be taken in the handler to locks not held while calling
usb_unlink_urb()
To prevent a race with resubmission, this patch exposes
usbcore's infrastructure for blocking submission, uses it
and so drops the lock without causing a race in usbhid.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index cd9b3a2cd8a7..9d912bfdcffe 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -681,6 +681,27 @@ void usb_unpoison_urb(struct urb *urb)
 EXPORT_SYMBOL_GPL(usb_unpoison_urb);
 
 /**
+ * usb_block_urb - reliably prevent further use of an URB
+ * @urb: pointer to URB to be blocked, may be NULL
+ *
+ * After the routine has run, attempts to resubmit the URB will fail
+ * with error -EPERM.  Thus even if the URB's completion handler always
+ * tries to resubmit, it will not succeed and the URB will become idle.
+ *
+ * The URB must not be deallocated while this routine is running.  In
+ * particular, when a driver calls this routine, it must insure that the
+ * completion handler cannot deallocate the URB.
+ */
+void usb_block_urb(struct urb *urb)
+{
+	if (!urb)
+		return;
+
+	atomic_inc(&urb->reject);
+}
+EXPORT_SYMBOL_GPL(usb_block_urb);
+
+/**
  * usb_kill_anchored_urbs - cancel transfer requests en masse
  * @anchor: anchor the requests are bound to
  *