From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424446AbWKJWSZ (ORCPT ); Fri, 10 Nov 2006 17:18:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1424452AbWKJWSZ (ORCPT ); Fri, 10 Nov 2006 17:18:25 -0500 Received: from mx1.redhat.com ([66.187.233.31]:23486 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S1424446AbWKJWSY (ORCPT ); Fri, 10 Nov 2006 17:18:24 -0500 Message-ID: <4554FAAB.1070409@redhat.com> Date: Fri, 10 Nov 2006 16:18:19 -0600 From: Eric Sandeen User-Agent: Thunderbird 1.5.0.8 (X11/20061107) MIME-Version: 1.0 To: Linux Kernel Mailing List Subject: [PATCH 2.6.19] Fix oops on ext3 directory corruption (resend from -mm) Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org (resend for 2.6.19 consideration, it's in -mm today) These were found using the infamous fsfuzzer tool. There may be security implications of this as well, and although I wouldn't probably judge it as high risk, there is some potential for mischief. First, we had a corrupted directory that was never checked for consistency... it was corrupt, and pointed to another bad "entry" of length 0. The for() loop looped forever, since the length of ext3_next_entry(de) was 0, and we kept looking at the same pointer over and over and over and over... I modeled this check and subsequent action on what is done for other directory types in ext3_readdir... Next we had a root directory inode which had a corrupted size, claimed to be > 200M on a 4M filesystem. There was only really 1 block in the directory, but because the size was so large, readdir kept coming back for more, spewing thousands of printk's along the way. Per Andreas' suggestion, if we're in this read error condition and we're trying to read an offset which is greater than i_blocks worth of bytes, stop trying, and break out of the loop. With these two changes fsfuzz test survives quite well on ext3. Signed-off-by: Eric Sandeen Index: linux-2.6.18/fs/ext3/namei.c =================================================================== --- linux-2.6.18.orig/fs/ext3/namei.c +++ linux-2.6.18/fs/ext3/namei.c @@ -551,6 +551,15 @@ static int htree_dirblock_to_tree(struct dir->i_sb->s_blocksize - EXT3_DIR_REC_LEN(0)); for (; de < top; de = ext3_next_entry(de)) { + if (!ext3_check_dir_entry("htree_dirblock_to_tree", dir, de, bh, + (block<i_sb)) + +((char *)de - bh->b_data))) { + /* On error, skip the f_pos to the next block. */ + dir_file->f_pos = (dir_file->f_pos | + (dir->i_sb->s_blocksize - 1)) + 1; + brelse (bh); + return count; + } ext3fs_dirhash(de->name, de->name_len, hinfo); if ((hinfo->hash < start_hash) || ((hinfo->hash == start_hash) && Index: linux-2.6.18/fs/ext3/dir.c =================================================================== --- linux-2.6.18.orig/fs/ext3/dir.c +++ linux-2.6.18/fs/ext3/dir.c @@ -151,6 +151,9 @@ static int ext3_readdir(struct file * fi ext3_error (sb, "ext3_readdir", "directory #%lu contains a hole at offset %lu", inode->i_ino, (unsigned long)filp->f_pos); + /* corrupt size? Maybe no more blocks to read */ + if (filp->f_pos > inode->i_blocks << 9) + break; filp->f_pos += sb->s_blocksize - offset; continue; }