ext4: fix corruption when online resizing a 1K bigalloc fs

commit 0aeaa2559d6d53358fca3e3fce73807367adca74 upstream.

When a backup superblock is updated in update_backups(), the primary
superblock's offset in the group (that is, sbi->s_sbh->b_blocknr) is used
as the backup superblock's offset in its group. However, when the block
size is 1K and bigalloc is enabled, the two offsets are not equal. This
causes the backup group descriptors to be overwritten by the superblock
in update_backups(). Moreover, if meta_bg is enabled, the file system will
be corrupted because this feature uses backup group descriptors.

To solve this issue, we use a more accurate ext4_group_first_block_no() as
the offset of the backup superblock in its group.

Fixes: d77147ff443b ("ext4: add support for online resizing with bigalloc")
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20221117040341.1380702-4-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 62bbfe8960f3b2d84bb148b394b549501292f94d..405c68085055fec398663663e95bc16732cd7faf 100644 (file)
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1557,8 +1557,8 @@ exit_journal:
                int meta_bg = ext4_has_feature_meta_bg(sb);
                sector_t old_gdb = 0;
 
-               update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
-                              sizeof(struct ext4_super_block), 0);
+               update_backups(sb, ext4_group_first_block_no(sb, 0),
+                              (char *)es, sizeof(struct ext4_super_block), 0);
                for (; gdb_num <= gdb_num_end; gdb_num++) {
                        struct buffer_head *gdb_bh;
 
@@ -1769,7 +1769,7 @@ errout:
                if (test_opt(sb, DEBUG))
                        printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
                               "blocks\n", ext4_blocks_count(es));
-               update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr,
+               update_backups(sb, ext4_group_first_block_no(sb, 0),
                               (char *)es, sizeof(struct ext4_super_block), 0);
        }
        return err;