Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751517Ab1CPBVS (ORCPT ); Tue, 15 Mar 2011 21:21:18 -0400 Received: from lon1-post-2.mail.demon.net ([195.173.77.149]:33977 "EHLO lon1-post-2.mail.demon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750975Ab1CPBVO (ORCPT ); Tue, 15 Mar 2011 21:21:14 -0400 Message-ID: <4D801078.5090104@lougher.demon.co.uk> Date: Wed, 16 Mar 2011 01:20:56 +0000 From: Phillip Lougher User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: linux-fsdevel@vger.kernel.org CC: Linux Kernel Development Subject: [PATCH] Squashfs: handle corruption of directory structure Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2966 Lines: 93 Handle the rare case where a directory metadata block is uncompressed and corrupted, leading to a kernel oops in directory scanning (memcpy). Normally corruption is detected at the decompression stage and dealt with then, however, this will not happen if: - metadata isn't compressed (users can optionally request no metadata compression), or - the compressed metadata block was larger than the original, in which case the uncompressed version was used, or - the data was corrupt after decompression This patch fixes this by adding some sanity checks against known maximum values. Signed-off-by: Phillip Lougher --- fs/squashfs/dir.c | 9 +++++++++ fs/squashfs/namei.c | 12 ++++++++++++ 2 files changed, 21 insertions(+), 0 deletions(-) diff --git a/fs/squashfs/dir.c b/fs/squashfs/dir.c index 0dc340a..3f79cd1 100644 --- a/fs/squashfs/dir.c +++ b/fs/squashfs/dir.c @@ -172,6 +172,11 @@ static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir) length += sizeof(dirh); dir_count = le32_to_cpu(dirh.count) + 1; + + /* dir_count should never be larger than 256 */ + if (dir_count > 256) + goto failed_read; + while (dir_count--) { /* * Read directory entry. @@ -183,6 +188,10 @@ static int squashfs_readdir(struct file *file, void *dirent, filldir_t filldir) size = le16_to_cpu(dire->size) + 1; + /* size should never be larger than SQUASHFS_NAME_LEN */ + if (size > SQUASHFS_NAME_LEN) + goto failed_read; + err = squashfs_read_metadata(inode->i_sb, dire->name, &block, &offset, size); if (err < 0) diff --git a/fs/squashfs/namei.c b/fs/squashfs/namei.c index 7a9464d..5d922a6 100644 --- a/fs/squashfs/namei.c +++ b/fs/squashfs/namei.c @@ -176,6 +176,11 @@ static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry, length += sizeof(dirh); dir_count = le32_to_cpu(dirh.count) + 1; + + /* dir_count should never be larger than 256 */ + if (dir_count > 256) + goto data_error; + while (dir_count--) { /* * Read directory entry. @@ -187,6 +192,10 @@ static struct dentry *squashfs_lookup(struct inode *dir, struct dentry *dentry, size = le16_to_cpu(dire->size) + 1; + /* size should never be larger than SQUASHFS_NAME_LEN */ + if (size > SQUASHFS_NAME_LEN) + goto data_error; + err = squashfs_read_metadata(dir->i_sb, dire->name, &block, &offset, size); if (err < 0) @@ -228,6 +237,9 @@ exit_lookup: d_add(dentry, inode); return ERR_PTR(0); +data_error: + err = -EIO; + read_failure: ERROR("Unable to read directory block [%llx:%x]\n", squashfs_i(dir)->start + msblk->directory_table, -- 1.7.1 -- 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/