From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753628AbeE3Lsn (ORCPT ); Wed, 30 May 2018 07:48:43 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60638 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751624AbeE3LG4 (ORCPT ); Wed, 30 May 2018 07:06:56 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Wen Xu" , "Theodore Ts'o" Date: Wed, 30 May 2018 11:52:41 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 006/153] ext4: fail ext4_iget for root directory if unallocated In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.102-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o commit 8e4b5eae5decd9dfe5a4ee369c22028f90ab4c44 upstream. If the root directory has an i_links_count of zero, then when the file system is mounted, then when ext4_fill_super() notices the problem and tries to call iput() the root directory in the error return path, ext4_evict_inode() will try to free the inode on disk, before all of the file system structures are set up, and this will result in an OOPS caused by a NULL pointer dereference. This issue has been assigned CVE-2018-1092. https://bugzilla.kernel.org/show_bug.cgi?id=199179 https://bugzilla.redhat.com/show_bug.cgi?id=1560777 Reported-by: Wen Xu Signed-off-by: Theodore Ts'o [bwh: Backported to 3.2: - Use EIO instead of EFSCORRUPTED - Adjust context] Signed-off-by: Ben Hutchings --- --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3902,6 +3902,13 @@ struct inode *ext4_iget(struct super_blo if (ret < 0) goto bad_inode; raw_inode = ext4_raw_inode(&iloc); + + if ((ino == EXT4_ROOT_INO) && (raw_inode->i_links_count == 0)) { + EXT4_ERROR_INODE(inode, "root inode unallocated"); + ret = -EIO; + goto bad_inode; + } + inode->i_mode = le16_to_cpu(raw_inode->i_mode); inode->i_uid = (uid_t)le16_to_cpu(raw_inode->i_uid_low); inode->i_gid = (gid_t)le16_to_cpu(raw_inode->i_gid_low);