From 21bad2b6797f387756af4480d338c0b877c86ba0 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Fri, 2 Oct 2020 14:47:25 -0400 Subject: [PATCH] resize2fs: prevent block group descriptors from overflowing the first bg For 1k block file systems, resizing a file system larger than 1073610752 blocks will result in the size of the block group descriptors to be so large that it will overlap with the backup superblock in block group #1. This problem can be reproduced via: mke2fs -t ext4 /tmp/foo.img 200M resize2fs /tmp/foo.img 1T e2fsck -f /tmp/foo.img https://github.com/tytso/e2fsprogs/issues/50 Signed-off-by: Theodore Ts'o --- resize/main.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/resize/main.c b/resize/main.c index a0c31c0..5e771d2 100644 --- a/resize/main.c +++ b/resize/main.c @@ -269,6 +269,8 @@ int main (int argc, char ** argv) long sysval; int len, mount_flags; char *mtpt, *undo_file = NULL; + dgrp_t new_group_desc_count; + unsigned long new_desc_blocks; #ifdef ENABLE_NLS setlocale(LC_MESSAGES, ""); @@ -528,6 +530,18 @@ int main (int argc, char ** argv) exit(1); } } + new_group_desc_count = ext2fs_div64_ceil(new_size - + fs->super->s_first_data_block, + EXT2_BLOCKS_PER_GROUP(fs->super)); + new_desc_blocks = ext2fs_div_ceil(new_group_desc_count, + EXT2_DESC_PER_BLOCK(fs->super)); + if ((new_desc_blocks + fs->super->s_first_data_block) > + EXT2_BLOCKS_PER_GROUP(fs->super)) { + com_err(program_name, 0, + _("New size results in too many block group " + "descriptors.\n")); + exit(1); + } if (!force && new_size < min_size) { com_err(program_name, 0, -- 1.8.3.1