[PATCH 5.19 132/717] ext4: fix dir corruption when ext4_dx_add_entry() fails

Greg Kroah-Hartman
2022-10-22T08:08:14Z

From: Zhihao Cheng <chengzhihao1@huawei.com>

commit 7177dd009c7c04290891e9a534cd47d1b620bd04 upstream.

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

Fix it by marking inode dirty directly inside ext4_append().
Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216466
Cc: stable@vger.kernel.org
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220911045204.516460-1-chengzhihao1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/namei.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -85,15 +85,20 @@ static struct buffer_head *ext4_append(h
return bh;
inode->i_size += inode->i_sb->s_blocksize;
EXT4_I(inode)->i_disksize = inode->i_size;
+ err = ext4_mark_inode_dirty(handle, inode);
+ if (err)
+ goto out;
BUFFER_TRACE(bh, "get_write_access");
err = ext4_journal_get_write_access(handle, inode->i_sb, bh,
EXT4_JTR_NONE);
- if (err) {
- brelse(bh);
- ext4_std_error(inode->i_sb, err);
- return ERR_PTR(err);
- }
+ if (err)
+ goto out;
return bh;
+
+out:
+ brelse(bh);
+ ext4_std_error(inode->i_sb, err);
+ return ERR_PTR(err);
}

static int ext4_dx_csum_verify(struct inode *inode,