linux-kernel - Re: [PATCH] USB: don't read past config->interface[] if usb_control_msg() fails in usb_reset

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Date:	Tue, 09 Feb 2010 17:01:53 +0100
From:	Roel Kluin <roel.kluin@...il.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Greg Kroah-Hartman <gregkh@...e.de>, sarah.a.sharp@...ux.intel.com,
	linux-usb@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] USB: don't read past config->interface[] if usb_control_msg()
 fails in usb_reset_configuration()

After the loop `for (i = 0; i < config->desc.bNumInterfaces; i++)' if no
break occurred, i equals config->desc.bNumInterfaces. so if
usb_control_msg() failed then after goto reset_old_alts we read from
config->interface[config->desc.bNumInterfaces].
We can safely decrement i as well if the break occurred.

Signed-off-by: Roel Kluin <roel.kluin@...il.com>
Acked-by: Alan Stern <stern@...land.harvard.edu>
---

> You correctly identified a problem, but your fix is wrong -- or at 
> least, it is much too complicated.

Ok,

 drivers/usb/core/message.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 9bc95fe..1a48aac 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1471,7 +1471,7 @@ int usb_reset_configuration(struct usb_device *dev)
 	/* If not, reinstate the old alternate settings */
 	if (retval < 0) {
 reset_old_alts:
-		for (; i >= 0; i--) {
+		for (i--; i >= 0; i--) {
 			struct usb_interface *intf = config->interface[i];
 			struct usb_host_interface *alt;
 
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