From: Bjørn Mork <bjorn@mork.no>
Date: Sun, 12 Jan 2014 20:48:53 +0000 (+0100)
Subject: usb: cdc-wdm: resp_count can be 0 even if WDM_READ is set
X-Git-Tag: v3.14-rc1~148^2~8
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f563926fed982f26b391ca42493f55f2447f1b0a;p=pandora-kernel.git

usb: cdc-wdm: resp_count can be 0 even if WDM_READ is set

Do not decrement resp_count if it's already 0.

We set resp_count to 0 when the device is closed.  The next open and
read will try to clear the WDM_READ flag if there was leftover data
in the read buffer. This fix is necessary to prevent resubmitting
the read URB in a tight loop because resp_count becomes negative.

The bug can easily be triggered from userspace by not reading all
data in the read buffer, and then closing and reopening the chardev.

Fixes: 8dd5cd5395b9 ("usb: cdc-wdm: avoid hanging on zero length reads")
Cc: <stable@vger.kernel.org> # 3.13
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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