tree 0251d98a74b0da9565299b7414280bafa17d14ca
parent 1c1052fd590ba1ec7f4ca70f237a876ab1cc4ae5
author Oleksij Rempel <linux@rempel-privat.de> 1374413779 +0200
committer Matthias Kaehlcke <mka@google.com> 1433366105 -0700

xhci: fix null pointer dereference on ring_doorbell_for_active_rings

commit d66eaf9f89502971fddcb0de550b01fa6f409d83 upstream.

in some cases where device is attched to xhci port and do not responding,
for example ath9k_htc with stalled firmware, kernel will
crash on ring_doorbell_for_active_rings.
This patch check if pointer exist before it is used.

This patch should be backported to kernels as old as 2.6.35, that
contain the commit e9df17eb1408cfafa3d1844bfc7f22c7237b31b8 "USB: xhci:
Correct assumptions about number of rings per endpoint"

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>