linux-kernel - Re: [PATCH RFC v11 12/19] dm: add finalize hook to target

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Message-ID: <CAHC9VhTC0+p9sgeEjCYBZKFu9FcPj3U5zQ7eqBOfwvg9Kd=vwA@mail.gmail.com>
Date:   Wed, 1 Nov 2023 20:41:12 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Fan Wu <wufan@...ux.microsoft.com>, corbet@....net,
        zohar@...ux.ibm.com, jmorris@...ei.org, serge@...lyn.com,
        tytso@....edu, ebiggers@...nel.org, axboe@...nel.dk,
        agk@...hat.com, snitzer@...nel.org, eparis@...hat.com
Cc:     linux-doc@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, linux-block@...r.kernel.org,
        dm-devel@...hat.com, audit@...r.kernel.org,
        roberto.sassu@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v11 12/19] dm: add finalize hook to target_type

On Mon, Oct 23, 2023 at 11:52 PM Paul Moore <paul@...l-moore.com> wrote:
> On Oct  4, 2023 Fan Wu <wufan@...ux.microsoft.com> wrote:
> >
> > This patch adds a target finalize hook.
> >
> > The hook is triggered just before activating an inactive table of a
> > mapped device. If it returns an error the __bind get cancelled.
> >
> > The dm-verity target will use this hook to attach the dm-verity's
> > roothash metadata to the block_device struct of the mapped device.
> >
> > Signed-off-by: Fan Wu <wufan@...ux.microsoft.com>
> > ---
> > v1-v10:
> >   + Not present
> > ---
> >  drivers/md/dm.c               | 12 ++++++++++++
> >  include/linux/device-mapper.h |  7 +++++++
> >  2 files changed, 19 insertions(+)
>
> We need an ACK and confirmation from Alasdair and/or Mike that this
> is the right approach.

A gentle ping with a reminder ...

For reference, the full patchset can be found on lore at the link below:

https://lore.kernel.org/linux-security-module/1696457386-3010-1-git-send-email-wufan@linux.microsoft.com/

> > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > index 64a1f306c96c..3be9cc35306d 100644
> > --- a/drivers/md/dm.c
> > +++ b/drivers/md/dm.c
> > @@ -2239,6 +2239,18 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> >               goto out;
> >       }
> >
> > +     for (unsigned int i = 0; i < t->num_targets; i++) {
> > +             struct dm_target *ti = dm_table_get_target(t, i);
> > +
> > +             if (ti->type->finalize) {
> > +                     ret = ti->type->finalize(ti);
> > +                     if (ret) {
> > +                             old_map = ERR_PTR(ret);
> > +                             goto out;
> > +                     }
> > +             }
> > +     }
> > +
> >       old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
> >       rcu_assign_pointer(md->map, (void *)t);
> >       md->immutable_target_type = dm_table_get_immutable_target_type(t);
> > diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> > index 69d0435c7ebb..4040e84a8ec7 100644
> > --- a/include/linux/device-mapper.h
> > +++ b/include/linux/device-mapper.h
> > @@ -160,6 +160,12 @@ typedef int (*dm_dax_zero_page_range_fn)(struct dm_target *ti, pgoff_t pgoff,
> >   */
> >  typedef size_t (*dm_dax_recovery_write_fn)(struct dm_target *ti, pgoff_t pgoff,
> >               void *addr, size_t bytes, struct iov_iter *i);
> > +/*
> > + * Returns:
> > + *  < 0 : error
> > + *  = 0 : success
> > + */
> > +typedef int (*dm_finalize_fn) (struct dm_target *target);
> >
> >  void dm_error(const char *message);
> >
> > @@ -209,6 +215,7 @@ struct target_type {
> >       dm_dax_direct_access_fn direct_access;
> >       dm_dax_zero_page_range_fn dax_zero_page_range;
> >       dm_dax_recovery_write_fn dax_recovery_write;
> > +     dm_finalize_fn finalize;
> >
> >       /* For internal device-mapper use. */
> >       struct list_head list;
> > --
> > 2.25.1

-- 
paul-moore.com