linux-kernel - Re: [PATCH v3] security/keys: rewrite big

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Message-ID: <CAHmME9r4Pag4ML-GVaKHFTZ_T_unhWg1LxVuEk6wKp006ZAFXg@mail.gmail.com>
Date:   Tue, 12 May 2020 20:33:11 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     David Howells <dhowells@...hat.com>
Cc:     keyrings@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        kernel-hardening@...ts.openwall.com,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v3] security/keys: rewrite big_key crypto to use library interface

On Tue, May 12, 2020 at 4:03 PM David Howells <dhowells@...hat.com> wrote:
>
> Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> > So long as that ->update function:
> > 1. Deletes the old on-disk data.
> > 2. Deletes the old key from the inode.
> > 3. Generates a new key using get_random_bytes.
> > 4. Stores that new key in the inode.
> > 5. Encrypts the updated data afresh with the new key.
> > 6. Puts the updated data onto disk,
> >
> > then this is fine with me, and feel free to have my Acked-by if you
> > want. But if it doesn't do that -- i.e. if it tries to reuse the old
> > key or similar -- then this isn't fine. But it sounds like from what
> > you've described that things are actually fine, in which case, I guess
> > it makes sense to apply your patch ontop of mine and commit these.
>
> Yep.  It calls big_key_destroy(), which clears away the old stuff just as when
> a key is being destroyed, then generic_key_instantiate() just as when a key is
> being set up.
>
> The key ID and the key metadata (ownership, perms, expiry) are maintained, but
> the payload is just completely replaced.

Okay, in that case, take my:

    Acked-by: Jason A. Donenfeld <Jason@...c4.com>

And then perhaps you can take both my patch and your addendum into keys-next.

Jason