[PATCH 1/2] libext2fs: Prevent allocating inode table from already used blocks

[Lukas Czerner <lczerner@redhat.com>]

Currently it's possible for ext2fs_allocate_group_table() to place inode
tables to blocks that are already occupied by different inode table.
This can be reproduced by resize2fs on the file system where we need to
move more than one inode table to a different location due to increase
in group descriptor blocks, inode and block bitmaps.

Best way I can reproduce this is to create big enough file system with
huge amount of inodes and without resize_inode

mke2fs -F -b 1024 -i 1024 -O ^resize_inode -t ext4 /dev/loop0 1024000
resize2fs /dev/loop0 10240000

e2fsck -fn /dev/loop0 | less
e2fsck 1.43.5 (04-Aug-2017)
ext2fs_check_desc: Corrupt group descriptor: bad block for inode table
e2fsck: Group descriptors look bad... trying backup blocks...
e2fsck: The journal superblock is corrupt while checking journal for /dev/loop0
e2fsck: Cannot proceed with file system check
Superblock has an invalid journal (inode 8).
Clear? no

/dev/loop0: ********** WARNING: Filesystem still has errors **********

None of the settings are strictly necessary and it can be reproducer in
various ways. This is just an example of one easy way to reproduce this.

This bug was introduced with commit fccdbac39454 ("libext2fs: optimize
ext2fs_allocate_group_table()") and is caused by the fact that wrong
bitmap is used to mark the blocks as used.

Fix this by using ext2fs_mark_block_bitmap_range2() in both (flex_bg and
non flex_bg) cases and handle flex_bg case manually instead of relying
on ext2fs_block_alloc_stats_range() because there is no way in that
function to use different bitmap than fs->block_map.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 lib/ext2fs/alloc_tables.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/lib/ext2fs/alloc_tables.c b/lib/ext2fs/alloc_tables.c
index da0b15b..407283f 100644
--- a/lib/ext2fs/alloc_tables.c
+++ b/lib/ext2fs/alloc_tables.c
@@ -222,12 +222,32 @@ errcode_t ext2fs_allocate_group_table(ext2_filsys fs, dgrp_t group,
 						bmap, &new_blk);
 		if (retval)
 			return retval;
-		if (flexbg_size)
-			ext2fs_block_alloc_stats_range(fs, new_blk,
-				       fs->inode_blocks_per_group, +1);
-		else
-			ext2fs_mark_block_bitmap_range2(fs->block_map,
-					new_blk, fs->inode_blocks_per_group);
+
+		ext2fs_mark_block_bitmap_range2(bmap,
+			new_blk, fs->inode_blocks_per_group);
+		if (flexbg_size) {
+			blk64_t num, blk;
+			num = fs->inode_blocks_per_group;
+			blk = new_blk;
+			while (num) {
+				int gr = ext2fs_group_of_blk2(fs, blk);
+				last_blk = ext2fs_group_last_block2(fs, gr);
+				blk64_t n = num;
+
+				if (blk + num > last_blk)
+					n = last_blk - blk + 1;
+
+				ext2fs_bg_free_blocks_count_set(fs, gr,
+					ext2fs_bg_free_blocks_count(fs, gr) -
+					n/EXT2FS_CLUSTER_RATIO(fs));
+				ext2fs_bg_flags_clear(fs, gr,
+					EXT2_BG_BLOCK_UNINIT);
+				ext2fs_group_desc_csum_set(fs, gr);
+				ext2fs_free_blocks_count_add(fs->super, -n);
+				blk += n;
+				num -= n;
+			}
+		}
 		ext2fs_inode_table_loc_set(fs, group, new_blk);
 	}
 	ext2fs_group_desc_csum_set(fs, group);
-- 
2.7.5