From a7a6126b94b9b6b0f88b5a5cc90d069974c89901 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Sat, 6 Mar 2021 23:08:12 -0500
Subject: [PATCH 24/46] resize2fs: avoid allocating over the MMP block
Content-Type: text/plain

When resizing past the point where the reserve inode has reserved
space for the block group descriptors to expand, and resize2fs (in an
offline resize) needs to move the allocation bitmaps and/or inode
table around, it's possible for resize2fs to allocate over the MMP
block, which would be bad.

Prevent this from happening by reserving the MMP block as a file
system metadata block (which it is) in resize2fs's accounting.

Addresses-Debian-Bug: #984472
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 resize/resize2fs.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/resize/resize2fs.c b/resize/resize2fs.c
index 26050fec..e8401e79 100644
--- a/resize/resize2fs.c
+++ b/resize/resize2fs.c
@@ -1176,6 +1176,11 @@ static errcode_t mark_table_blocks(ext2_filsys fs,
 		if (blk)
 			ext2fs_mark_block_bitmap2(bmap, blk);
 	}
+	/* Reserve the MMP block */
+	if (ext2fs_has_feature_mmp(fs->super) &&
+	    fs->super->s_mmp_block > fs->super->s_first_data_block &&
+	    fs->super->s_mmp_block < ext2fs_blocks_count(fs->super))
+		ext2fs_mark_block_bitmap2(bmap, fs->super->s_mmp_block);
 	return 0;
 }
 
-- 
2.35.1