linux-kernel - Re: [PATCH v2] ext4: Fix dir corruption when ext4_dx_add

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Date:   Thu, 29 Sep 2022 23:19:32 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     adilger.kernel@...ger.ca, chengzhihao1@...wei.com, jack@...e.cz
Cc:     "Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com
Subject: Re: [PATCH v2] ext4: Fix dir corruption when ext4_dx_add_entry() fails

On Sun, 11 Sep 2022 12:52:04 +0800, Zhihao Cheng wrote:
> Following process may lead to fs corruption:
> 1. ext4_create(dir/foo)
>  ext4_add_nondir
>   ext4_add_entry
>    ext4_dx_add_entry
>      a. add_dirent_to_buf
>       ext4_mark_inode_dirty
>       ext4_handle_dirty_metadata   // dir inode bh is recorded into journal
>      b. ext4_append    // dx_get_count(entries) == dx_get_limit(entries)
>        ext4_bread(EXT4_GET_BLOCKS_CREATE)
>         ext4_getblk
>          ext4_map_blocks
>           ext4_ext_map_blocks
>             ext4_mb_new_blocks
>              dquot_alloc_block
>               dquot_alloc_space_nodirty
>                inode_add_bytes    // update dir's i_blocks
>             ext4_ext_insert_extent
> 	     ext4_ext_dirty  // record extent bh into journal
>               ext4_handle_dirty_metadata(bh)
> 	      // record new block into journal
>        inode->i_size += inode->i_sb->s_blocksize   // new size(in mem)
>      c. ext4_handle_dirty_dx_node(bh2)
> 	// record dir's new block(dx_node) into journal
>      d. ext4_handle_dirty_dx_node((frame - 1)->bh)
>      e. ext4_handle_dirty_dx_node(frame->bh)
>      f. do_split    // ret err!
>      g. add_dirent_to_buf
> 	 ext4_mark_inode_dirty(dir)  // update raw_inode on disk(skipped)
> 2. fsck -a /dev/sdb
>  drop last block(dx_node) which beyonds dir's i_size.
>   /dev/sdb: recovering journal
>   /dev/sdb contains a file system with errors, check forced.
>   /dev/sdb: Inode 12, end of extent exceeds allowed value
> 	(logical block 128, physical block 3938, len 1)
> 3. fsck -fn /dev/sdb
>  dx_node->entry[i].blk > dir->i_size
>   Pass 2: Checking directory structure
>   Problem in HTREE directory inode 12 (/dir): bad block number 128.
>   Clear HTree index? no
>   Problem in HTREE directory inode 12: block #3 has invalid depth (2)
>   Problem in HTREE directory inode 12: block #3 has bad max hash
>   Problem in HTREE directory inode 12: block #3 not referenced
> 
> [...]

Applied, thanks!

[1/1] ext4: Fix dir corruption when ext4_dx_add_entry() fails
      commit: 7a3584fd605e6a72036c5759a6e9ed2c46d14899

Best regards,
-- 
Theodore Ts'o <tytso@....edu>