From: Akira Fujita Subject: [PATCH 1/3] mke2fs: set upper limit to flex_bg count Date: Wed, 11 Jun 2014 08:37:22 +0000 Message-ID: <28989C0C9F1C0A428470D967B5FCED372A7E6D@BPXM22GP.gisp.nec.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: 8BIT Cc: Ext4 Developers List To: Theodore Tso Return-path: Received: from TYO200.gate.nec.co.jp ([210.143.35.50]:44697 "EHLO tyo200.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752219AbaFKJCs convert rfc822-to-8bit (ORCPT ); Wed, 11 Jun 2014 05:02:48 -0400 Received: from tyo201.gate.nec.co.jp ([10.7.69.201]) by tyo200.gate.nec.co.jp (8.13.8/8.13.4) with ESMTP id s5B8fw3r015954 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 11 Jun 2014 17:41:59 +0900 (JST) Content-Language: ja-JP Sender: linux-ext4-owner@vger.kernel.org List-ID: mke2fs -G option allows root user to set flex_bg count (power of 2). However ext4 has bad metadata layout if we specify more than or equal to 2^32 to mke2fs -G, because of the 32bit shift operation in ext2fs_allocate_group_table(). And the maximum block group count of ext4 is 2^32 -1 (ext4_group_t s_groups_count), so diallow more than 2^32 flex_bg count. Steps to reproduce: # mke2fs -t ext4 -G 4294967296 DEV # dumpe2fs DEV Flex block group size: 1 <----- flex_bg is 1! Group 0: (Blocks 0-32767) Checksum 0x4afd, unused inodes 7541 Primary superblock at 0, Group descriptors at 1-1 Reserved GDT blocks at 2-59 Block bitmap at 60 (+60), Inode bitmap at 61 (+61) Inode table at 62-533 (+62) 32228 free blocks, 7541 free inodes, 2 directories, 7541 unused inodes Free blocks: 540-32767 Free inodes: 12-7552 Group 1: (Blocks 32768-65535) [INODE_UNINIT] Checksum 0xc890, unused inodes 7552 Backup superblock at 32768, Group descriptors at 32769-32769 Reserved GDT blocks at 32770-32827 Block bitmap at 32828 (+60), Inode bitmap at 32829 (+61) Inode table at 32830-33301 (+62) 32234 free blocks, 7552 free inodes, 0 directories, 7552 unused inodes Free blocks: 33302-65535 Free inodes: 7553-15104 Signed-off-by: Akira Fujita --- misc/mke2fs.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/misc/mke2fs.c b/misc/mke2fs.c index b451cc3..b9145d1 100644 --- a/misc/mke2fs.c +++ b/misc/mke2fs.c @@ -1605,6 +1605,12 @@ profile_error: _("flex_bg size must be a power of 2")); exit(1); } + if (flex_bg_size > MAX_32_NUM) { + com_err(program_name, 0, + _("flex_bg size (%lu) must be less than" + " or equal to 2^31"), flex_bg_size); + exit(1); + } break; case 'i': inode_ratio = strtoul(optarg, &tmp, 0);