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>
Tue, 27 May 2014 22:04:09 +0000 (15:04 -0700)
commit140cb81ac8c625942a1d695875932c615767a526
treee4e3139dda91615156dc52524b5f4e23d85ac456
parente144ed28bed10684f9aaec6325ed974d53f76110
USB: cdc-acm: fix broken runtime suspend

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>
Cc: <stable@vger.kernel.org> # v2.6.27
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