Re: [PATCH] f2fs: validate compress cache inode only when enabled

[Chao Yu <chao@kernel.org>]

On 5/21/26 11:16, Wenjie Qi wrote:
> F2FS_COMPRESS_INO() uses NM_I(sbi)->max_nid as the synthetic inode
> number for the compressed page cache inode. That inode only exists when
> the compress_cache mount option is enabled.
> 
> When compress_cache is disabled, max_nid is outside the valid inode
> range. A corrupted directory entry that points to ino == max_nid should
> therefore be rejected by f2fs_check_nid_range(). However, is_meta_ino()
> currently treats F2FS_COMPRESS_INO() as a meta inode unconditionally,
> so f2fs_iget() bypasses do_read_inode() and its nid range check, and
> instantiates a fake internal inode instead.
> 
> Gate the compressed cache inode case on COMPRESS_CACHE, matching
> f2fs_init_compress_inode(). With compress_cache disabled, ino ==
> max_nid now follows the normal inode path and is rejected as an
> out-of-range nid.
> 

Cc: stable@kernel.org

> Fixes: 6ce19aff0b8c ("f2fs: compress: add compress_inode to cache compressed blocks")
> Signed-off-by: Wenjie Qi <qiwenjie@xiaomi.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,