Re: [PATCH] ocfs2: Add i_size check for dir

[Joseph Qi <joseph.qi@linux.alibaba.com>]

On 8/20/24 8:08 PM, Edward Adam Davis wrote:
> When the i_size of dir is too large, it will cause limit to overflow and
> be less than de_buf, ultimately resulting in last_de not being initialized
> and causing uaf issue.
> 
> Reported-and-tested-by: syzbot+5a64828fcc4c2ad9b04f@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
>  fs/ocfs2/dir.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
> index d620d4c53c6f..c308dba6d213 100644
> --- a/fs/ocfs2/dir.c
> +++ b/fs/ocfs2/dir.c
> @@ -3343,6 +3343,8 @@ static int ocfs2_find_dir_space_id(struct inode *dir, struct buffer_head *di_bh,
>  	unsigned long offset = 0;
>  	unsigned int rec_len, new_rec_len, free_space;
>  
> +	if (i_size_read(dir) > OCFS2_MAX_BLOCKSIZE)
> +		return -EINVAL;

Why OCFS2_MAX_BLOCKSIZE?
It seems that this is caused by a corrupted dir inode, since this is an
inline case, we may try best to make sure it won't exceeds block size?
i.e. dir->i_sb->s_blocksize.

Thanks,
Joseph

>  	/*
>  	 * This calculates how many free bytes we'd have in block zero, should
>  	 * this function force expansion to an extent tree.