Re: [PATCH V2] ext4: add casefolded feature check before setup encrypted info

[Eric Biggers]

On Fri, May 31, 2024 at 11:30:44AM +0800, 'Lizhi Xu' via syzkaller-bugs wrote:
> On Thu, 30 May 2024 20:11:33 -0700, Eric Biggers wrote:
> > > Due to the current file system not supporting the casefolded feature, only 
> > > i_crypt_info was initialized when creating encrypted information, without actually
> > > setting the sighash. Therefore, when creating an inode, if the system does not 
> > > support the casefolded feature, encrypted information will not be created.
> > > 
> > > Reported-by: syzbot+340581ba9dceb7e06fb3@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
> > > ---
> > >  fs/ext4/ialloc.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> > > index e9bbb1da2d0a..47b75589fdf4 100644
> > > --- a/fs/ext4/ialloc.c
> > > +++ b/fs/ext4/ialloc.c
> > > @@ -983,7 +983,8 @@ struct inode *__ext4_new_inode(struct mnt_idmap *idmap,
> > >  		ei->i_projid = make_kprojid(&init_user_ns, EXT4_DEF_PROJID);
> > >  
> > >  	if (!(i_flags & EXT4_EA_INODE_FL)) {
> > > -		err = fscrypt_prepare_new_inode(dir, inode, &encrypt);
> > > +		if (ext4_has_feature_casefold(inode->i_sb))
> > > +			err = fscrypt_prepare_new_inode(dir, inode, &encrypt);
> > >  		if (err)
> > >  			goto out;
> > 
> > No, this is not correct at all.  This just disables encryption on filesystems
> > with the casefold feature.
> If filesystems not support casefold feature, Why do I need to setup encrypted
> information when creating a directory? Can encrypted information not include *hash?

Encryption is a separate feature.  It is supported both with and without
casefold.

- Eric