linux-kernel - Re: [PATCH v3 3/3] ovl: validate superblock in OVL

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Message-ID: <ZNiG4WFcQRGL1dWx@righiandr-XPS-13-7390>
Date:   Sun, 13 Aug 2023 09:31:45 +0200
From:   Andrea Righi <andrea.righi@...onical.com>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Miklos Szeredi <miklos@...redi.hu>, linux-unionfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] ovl: validate superblock in OVL_FS()

On Sat, Aug 12, 2023 at 07:26:01PM +0300, Amir Goldstein wrote:
> On Fri, Aug 11, 2023 at 12:14 PM Amir Goldstein <amir73il@...il.com> wrote:
> >
> > On Mon, Jul 24, 2023 at 5:43 PM Miklos Szeredi <miklos@...redi.hu> wrote:
> > >
> > > On Sun, 21 May 2023 at 10:28, Andrea Righi <andrea.righi@...onical.com> wrote:
> > > >
> > > > When CONFIG_OVERLAY_FS_DEBUG is enabled add an explicit check to make
> > > > sure that OVL_FS() is always used with a valid overlayfs superblock.
> > > > Otherwise trigger a WARN_ON_ONCE().
> > > >
> > > > Reviewed-by: Amir Goldstein <amir73il@...il.com>
> > > > Signed-off-by: Andrea Righi <andrea.righi@...onical.com>
> > > > ---
> > > >  fs/overlayfs/ovl_entry.h | 12 ++++++++++++
> > > >  1 file changed, 12 insertions(+)
> > > >
> > > > diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
> > > > index b32c38fdf3c7..e156649d9c71 100644
> > > > --- a/fs/overlayfs/ovl_entry.h
> > > > +++ b/fs/overlayfs/ovl_entry.h
> > > > @@ -97,8 +97,20 @@ static inline struct mnt_idmap *ovl_upper_mnt_idmap(struct ovl_fs *ofs)
> > > >
> > > >  extern struct file_system_type ovl_fs_type;
> > > >
> > > > +static inline bool is_ovl_fs_sb(struct super_block *sb)
> > > > +{
> > > > +       return sb->s_type == &ovl_fs_type;
> > > > +}
> > > > +
> > > > +#ifdef CONFIG_OVERLAY_FS_DEBUG
> > > > +#define OVL_VALIDATE_SB(__sb)  WARN_ON_ONCE(!is_ovl_fs_sb(__sb))
> > > > +#else
> > > > +#define OVL_VALIDATE_SB(__sb)
> > > > +#endif
> > > > +
> > > >  static inline struct ovl_fs *OVL_FS(struct super_block *sb)
> > > >  {
> > > > +       OVL_VALIDATE_SB(sb);
> > >
> > > This could be written simply and naturally:
> > >
> > >     if (IS_ENABLED(CONFIG_OVERLAY_FS_DEBUG))
> > >          WARN_ON_ONCE(sb->s_type != &ovl_fs_type)
> > >
> >
> > Andrea,
> >
> > There is an inherent challenge with a cleanup series like this one
> > that touches many functions to avoid merge conflicts with other
> > devel branches. I did not try, but I expect there are conflicts
> > with the current overlayfs-next branch.
> >
> > I also see at least one new direct reference of sb->s_fs_info
> > in ovl_maybe_validate_verity().
> >
> > Please make sure to base your next submission on overlayfs-next
> > branch from git://git.kernel.org/pub/scm/linux/kernel/git/overlayfs/vfs.git.
> >
> > Once you do that, we could apply your patches to overlayfs-next
> > so they won't get stale again.
> 
> Nevermind, I had rebased overlayfs-next, so already applied your
> patches with the needed conflict resolutions and addressed Miklos' comment.

Sorry for the late response, I was on vacation (with a poor internet
connection). However, it looks like there's not much to do for me at
this point, thanks for taking care of this! :)

-Andrea

> 
> Thanks,
> Amir.