Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760865AbXKHKxl (ORCPT ); Thu, 8 Nov 2007 05:53:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759383AbXKHKxd (ORCPT ); Thu, 8 Nov 2007 05:53:33 -0500 Received: from [222.73.24.84] ([222.73.24.84]:53277 "EHLO song.cn.fujitsu.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1759238AbXKHKxc (ORCPT ); Thu, 8 Nov 2007 05:53:32 -0500 Message-ID: <4732EAB4.5070605@cn.fujitsu.com> Date: Thu, 08 Nov 2007 18:53:40 +0800 From: Miao Xie User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: tglx@linutronix.de CC: linux-kernel@vger.kernel.org Subject: [PATCH] time: fix sysfs_show_{available,current}_clocksources() buffer overflow problem Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2778 Lines: 96 Hi,every one. I found that there is a buffer overflow problem in the following code. Version: 2.6.24-rc2, File: kernel/time/clocksource.c:417-432 -------------------------------------------------------------------- static ssize_t sysfs_show_available_clocksources(struct sys_device *dev, char *buf) { struct clocksource *src; char *curr = buf; spin_lock_irq(&clocksource_lock); list_for_each_entry(src, &clocksource_list, list) { curr += sprintf(curr, "%s ", src->name); } spin_unlock_irq(&clocksource_lock); curr += sprintf(curr, "\n"); return curr - buf; } ----------------------------------------------------------------------- sysfs_show_current_clocksources() also has the same problem though in practice the size of current clocksource's name won't exceed PAGE_SIZE. I fix the bug by using snprintf according to the specification of the kernel (Version:2.6.24-rc2,File:Documentation/filesystems/sysfs.txt) Fix sysfs_show_available_clocksources() and sysfs_show_current_clocksources() buffer overflow problem with snprintf(). Signed-off-by: Miao Xie --- kernel/time/clocksource.c | 19 ++++++++++--------- 1 files changed, 10 insertions(+), 9 deletions(-) diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index c8a9d13..5d5926f 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -342,15 +342,13 @@ void clocksource_change_rating(struct clocksource *cs, int rating) static ssize_t sysfs_show_current_clocksources(struct sys_device *dev, char *buf) { - char *curr = buf; + ssize_t count = 0; spin_lock_irq(&clocksource_lock); - curr += sprintf(curr, "%s ", curr_clocksource->name); + count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); spin_unlock_irq(&clocksource_lock); - curr += sprintf(curr, "\n"); - - return curr - buf; + return count; } /** @@ -418,17 +416,20 @@ static ssize_t sysfs_show_available_clocksources(struct sys_device *dev, char *buf) { struct clocksource *src; - char *curr = buf; + ssize_t count = 0; spin_lock_irq(&clocksource_lock); list_for_each_entry(src, &clocksource_list, list) { - curr += sprintf(curr, "%s ", src->name); + count += snprintf(buf + count, + max((ssize_t)PAGE_SIZE - count, (ssize_t)0), + "%s ", src->name); } spin_unlock_irq(&clocksource_lock); - curr += sprintf(curr, "\n"); + count += snprintf(buf + count, + max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); - return curr - buf; + return count; } /* -- 1.5.3 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/