From: Akira Fujita Date: Sun, 6 Jul 2014 02:14:08 +0000 (-0400) Subject: mke2fs: set upper limit to flex_bg count X-Git-Tag: v1.42.11~27 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a131053ef05e2c4dd3c9a2880fc61423dac39eb1;p=thirdparty%2Fe2fsprogs.git mke2fs: set upper limit to flex_bg count 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 Signed-off-by: Theodore Ts'o Reviewed-by: "Darrick J. Wong" --- diff --git a/misc/mke2fs.c b/misc/mke2fs.c index d5e16c03a..a08709d1e 100644 --- a/misc/mke2fs.c +++ b/misc/mke2fs.c @@ -1572,6 +1572,12 @@ 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);