linux-kernel - [PATCH] wusb: fix find_first_zero

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Message-Id: <1299065728-6124-1-git-send-email-akinobu.mita@gmail.com>
Date:	Wed,  2 Mar 2011 20:35:28 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Akinobu Mita <akinobu.mita@...il.com>, linux-usb@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [PATCH] wusb: fix find_first_zero_bit() return value check

In wusb_cluster_id_get(), if no zero bits exist in wusb_cluster_id_table,
find_first_zero_bit() returns CLUSTER_IDS.

But it is impossible to detect that the bitmap is full because there
is an off-by-one error in the return value check.  It will cause
unexpected memory access by setting bit out of wusb_cluster_id_table
bitmap, and caller will get wrong cluster id.

Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
Cc: linux-usb@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/usb/wusbcore/wusbhc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/usb/wusbcore/wusbhc.c b/drivers/usb/wusbcore/wusbhc.c
index 2054d4e..0faca16 100644
--- a/drivers/usb/wusbcore/wusbhc.c
+++ b/drivers/usb/wusbcore/wusbhc.c
@@ -320,7 +320,7 @@ u8 wusb_cluster_id_get(void)
 	u8 id;
 	spin_lock(&wusb_cluster_ids_lock);
 	id = find_first_zero_bit(wusb_cluster_id_table, CLUSTER_IDS);
-	if (id > CLUSTER_IDS) {
+	if (id >= CLUSTER_IDS) {
 		id = 0;
 		goto out;
 	}
-- 
1.7.4

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