From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941333AbcKNDlZ (ORCPT ); Sun, 13 Nov 2016 22:41:25 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45270 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752823AbcKNCER (ORCPT ); Sun, 13 Nov 2016 21:04:17 -0500 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, "Theodore Ts'o" , "Vegard Nossum" Date: Mon, 14 Nov 2016 00:14:20 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 042/346] ext4: validate s_reserved_gdt_blocks on mount 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 3.16.39-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o commit 5b9554dc5bf008ae7f68a52e3d7e76c0920938a2 upstream. If s_reserved_gdt_blocks is extremely large, it's possible for ext4_init_block_bitmap(), which is called when ext4 sets up an uninitialized block bitmap, to corrupt random kernel memory. Add the same checks which e2fsck has --- it must never be larger than blocksize / sizeof(__u32) --- and then add a backup check in ext4_init_block_bitmap() in case the superblock gets modified after the file system is mounted. Reported-by: Vegard Nossum Signed-off-by: Theodore Ts'o [bwh: Backported to 3.16: - Use EIO instead of EFSCORRUPTED - Adjust context] Signed-off-by: Ben Hutchings --- fs/ext4/balloc.c | 3 +++ fs/ext4/super.c | 7 +++++++ 2 files changed, 10 insertions(+) --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -209,6 +209,9 @@ static int ext4_init_block_bitmap(struct memset(bh->b_data, 0, sb->s_blocksize); bit_max = ext4_num_base_meta_clusters(sb, block_group); + if ((bit_max >> 3) >= bh->b_size) + return -EIO; + for (bit = 0; bit < bit_max; bit++) ext4_set_bit(bit, bh->b_data); --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3644,6 +3644,13 @@ static int ext4_fill_super(struct super_ goto failed_mount; } + if (le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) > (blocksize / 4)) { + ext4_msg(sb, KERN_ERR, + "Number of reserved GDT blocks insanely large: %d", + le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks)); + goto failed_mount; + } + if (sb->s_blocksize != blocksize) { /* Validate the filesystem blocksize */ if (!sb_set_blocksize(sb, blocksize)) {