ext4: Fix reusing stale buffer heads from last failed mounting

Following process makes ext4 load stale buffer heads from last failed
mounting in a new mounting operation:
mount_bdev
 ext4_fill_super
 | ext4_load_and_init_journal
 |  ext4_load_journal
 |   jbd2_journal_load
 |    load_superblock
 |     journal_get_superblock
 |      set_buffer_verified(bh) // buffer head is verified
 |   jbd2_journal_recover // failed caused by EIO
 | goto failed_mount3a // skip 'sb->s_root' initialization
 deactivate_locked_super
  kill_block_super
   generic_shutdown_super
    if (sb->s_root)
    // false, skip ext4_put_super->invalidate_bdev->
    // invalidate_mapping_pages->mapping_evict_folio->
    // filemap_release_folio->try_to_free_buffers, which
    // cannot drop buffer head.
   blkdev_put
    blkdev_put_whole
     if (atomic_dec_and_test(&bdev->bd_openers))
     // false, systemd-udev happens to open the device. Then
     // blkdev_flush_mapping->kill_bdev->truncate_inode_pages->
     // truncate_inode_folio->truncate_cleanup_folio->
     // folio_invalidate->block_invalidate_folio->
     // filemap_release_folio->try_to_free_buffers will be skipped,
     // dropping buffer head is missed again.

Second mount:
ext4_fill_super
 ext4_load_and_init_journal
  ext4_load_journal
   ext4_get_journal
    jbd2_journal_init_inode
     journal_init_common
      bh = getblk_unmovable
       bh = __find_get_block // Found stale bh in last failed mounting
      journal->j_sb_buffer = bh
   jbd2_journal_load
    load_superblock
     journal_get_superblock
      if (buffer_verified(bh))
      // true, skip journal->j_format_version = 2, value is 0
    jbd2_journal_recover
     do_one_pass
      next_log_block += count_tags(journal, bh)
      // According to journal_tag_bytes(), 'tag_bytes' calculating is
      // affected by jbd2_has_feature_csum3(), jbd2_has_feature_csum3()
      // returns false because 'j->j_format_version >= 2' is not true,
      // then we get wrong next_log_block. The do_one_pass may exit
      // early whenoccuring non JBD2_MAGIC_NUMBER in 'next_log_block'.

The filesystem is corrupted here, journal is partially replayed, and
new journal sequence number actually is already used by last mounting.

The invalidate_bdev() can drop all buffer heads even racing with bare
reading block device(eg. systemd-udev), so we can fix it by invalidating
bdev in error handling path in __ext4_fill_super().

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217171
Fixes: 25ed6e8a54df ("jbd2: enable journal clients to enable v2 checksumming")
Cc: stable@vger.kernel.org # v3.5
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230315013128.3911115-2-chengzhihao1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7f9b087..6a8c5c3 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1128,6 +1128,12 @@ static void ext4_blkdev_remove(struct ext4_sb_info *sbi)
        struct block_device *bdev;
        bdev = sbi->s_journal_bdev;
        if (bdev) {
+               /*
+                * Invalidate the journal device's buffers.  We don't want them
+                * floating about in memory - the physical journal device may
+                * hotswapped, and it breaks the `ro-after' testing code.
+                */
+               invalidate_bdev(bdev);
                ext4_blkdev_put(bdev);
                sbi->s_journal_bdev = NULL;
        }
@@ -1328,13 +1334,7 @@ static void ext4_put_super(struct super_block *sb)
        sync_blockdev(sb->s_bdev);
        invalidate_bdev(sb->s_bdev);
        if (sbi->s_journal_bdev && sbi->s_journal_bdev != sb->s_bdev) {
-               /*
-                * Invalidate the journal device's buffers.  We don't want them
-                * floating about in memory - the physical journal device may
-                * hotswapped, and it breaks the `ro-after' testing code.
-                */
                sync_blockdev(sbi->s_journal_bdev);
-               invalidate_bdev(sbi->s_journal_bdev);
                ext4_blkdev_remove(sbi);
        }
 
@@ -5655,6 +5655,7 @@ failed_mount:
        brelse(sbi->s_sbh);
        ext4_blkdev_remove(sbi);
 out_fail:
+       invalidate_bdev(sb->s_bdev);
        sb->s_fs_info = NULL;
        return err;
 }