From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753328Ab1JHH5I (ORCPT ); Sat, 8 Oct 2011 03:57:08 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:52233 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752219Ab1JHH5A (ORCPT ); Sat, 8 Oct 2011 03:57:00 -0400 Subject: [PATCH 04/28] ext4: Prevent stack overrun in ext4_file_open when recording last known mountpoint To: Andreas Dilger , Theodore Tso , "Darrick J. Wong" From: "Darrick J. Wong" Cc: Sunil Mushran , Martin K Petersen , Greg Freemyer , Amir Goldstein , linux-kernel , Andi Kleen , Mingming Cao , Joel Becker , linux-fsdevel , linux-ext4@vger.kernel.org, Coly Li Date: Sat, 08 Oct 2011 00:54:10 -0700 Message-ID: <20111008075410.20506.47923.stgit@elm3c44.beaverton.ibm.com> In-Reply-To: <20111008075343.20506.23155.stgit@elm3c44.beaverton.ibm.com> References: <20111008075343.20506.23155.stgit@elm3c44.beaverton.ibm.com> User-Agent: StGit/0.15 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit x-cbid: 11100807-3270-0000-0000-000000B57A85 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In ext4_file_open, the filesystem records the mountpoint of the first file that is opened after mounting the filesystem. It does this by allocating a 64-byte stack buffer, calling d_path() to grab the mount point through which this file was accessed, and then memcpy()ing 64 bytes into the superblock's s_last_mounted field, starting from the return value of d_path(), which is stored as "cp". However, if cp > buf (which it frequently is since path components are prepended starting at the end of buf) then we can end up copying stack data into the superblock. Writing stack variables into the superblock doesn't sound like a great idea, so use strlcpy instead. Andi Kleen suggested using strlcpy instead of strncpy. Signed-off-by: Darrick J. Wong --- fs/ext4/file.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index e4095e9..9781099 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -181,8 +181,8 @@ static int ext4_file_open(struct inode * inode, struct file * filp) path.dentry = mnt->mnt_root; cp = d_path(&path, buf, sizeof(buf)); if (!IS_ERR(cp)) { - memcpy(sbi->s_es->s_last_mounted, cp, - sizeof(sbi->s_es->s_last_mounted)); + strlcpy(sbi->s_es->s_last_mounted, cp, + sizeof(sbi->s_es->s_last_mounted)); ext4_mark_super_dirty(sb); } }