USB: cdc-acm: fix broken runtime suspend
authorJohan Hovold <jhovold@gmail.com>
Mon, 26 May 2014 17:23:38 +0000 (19:23 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 26 Jun 2014 19:12:39 +0000 (15:12 -0400)
commit67e8477bd13b64ab4805dbd639f13192b49034ba
treea2276ff38d1c20a26ccfeb43f5027be1775762f4
parent1b3fe0068c8d5efd5d81ce6f5616d9cec1921e3a
USB: cdc-acm: fix broken runtime suspend

commit 140cb81ac8c625942a1d695875932c615767a526 upstream.

The current ACM runtime-suspend implementation is broken in several
ways:

Firstly, it buffers only the first write request being made while
suspended -- any further writes are silently dropped.

Secondly, writes being dropped also leak write urbs, which are never
reclaimed (until the device is unbound).

Thirdly, even the single buffered write is not cleared at shutdown
(which may happen before the device is resumed), something which can
lead to another urb leak as well as a PM usage-counter leak.

Fix this by implementing a delayed-write queue using urb anchors and
making sure to discard the queue properly at shutdown.

Fixes: 11ea859d64b6 ("USB: additional power savings for cdc-acm devices
that support remote wakeup")

Reported-by: Xiao Jin <jin.xiao@intel.com>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/class/cdc-acm.c
drivers/usb/class/cdc-acm.h