From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762318AbXK1Wyw (ORCPT ); Wed, 28 Nov 2007 17:54:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762055AbXK1Wxl (ORCPT ); Wed, 28 Nov 2007 17:53:41 -0500 Received: from mx2.suse.de ([195.135.220.15]:41989 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762045AbXK1Wxk (ORCPT ); Wed, 28 Nov 2007 17:53:40 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Miao Xie , Andrew Morton , Greg Kroah-Hartman Subject: [PATCH 6/6] sysfs: fix off-by-one error in fill_read_buffer() Date: Wed, 28 Nov 2007 14:52:20 -0800 Message-Id: <1196290340-28828-6-git-send-email-gregkh@suse.de> X-Mailer: git-send-email 1.5.3.4 In-Reply-To: <20071128224746.GA28410@kroah.com> References: <20071128224746.GA28410@kroah.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Miao Xie I found that there is a off-by-one problem in the following code. Version: 2.6.24-rc2 File: fs/sysfs/file.c:118-122 Function: fill_read_buffer -------------------------------------------------------------------- count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page); sysfs_put_active_two(attr_sd); BUG_ON(count > (ssize_t)PAGE_SIZE); -------------------------------------------------------------------- Because according to the specification of the sysfs and the implement of the show methods, the show methods return the number of bytes which would be generated for the given input, excluding the trailing null.So if the return value of the show methods equals PAGE_SIZE - 1, the buffer is full in fact. And if the return value equals PAGE_SIZE, the resulting string was already truncated,or buffer overflow occurred. This patch fixes an off-by-one error in fill_read_buffer. Signed-off-by: Miao Xie Signed-off-by: Andrew Morton Acked-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/file.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 27d1785..4045bdc 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -119,7 +119,11 @@ static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer sysfs_put_active_two(attr_sd); - BUG_ON(count > (ssize_t)PAGE_SIZE); + /* + * The code works fine with PAGE_SIZE return but it's likely to + * indicate truncated result or overflow in normal use cases. + */ + BUG_ON(count >= (ssize_t)PAGE_SIZE); if (count >= 0) { buffer->needs_read_fill = 0; buffer->count = count; -- 1.5.3.4