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

[Edward Adam Davis]

On Tue, 20 Aug 2024 20:44:37 +0800, Joseph Qi 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
> > ---
> >  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?
I think it is largest block size in ocfs2, therefore, if it is larger
than it, it must be incorrect, even though the value of i_size in dir
in the current issue is much larger than it (i_size_read(dir) is 0x900000000000100).
> 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.
You mean dir->i_sb->s_blocksize bigger than OCFS2_MAX_BLOCKSIZE?

BR,
Edward