linux-kernel - Re: [PATCH RESEND] KEYS: fix parsing invalid pkey info string

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Date:   Mon, 17 Dec 2018 15:21:07 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        ebiggers@...nel.org, James Morris James Morris <jmorris@...ei.org>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>
Cc:     David Howells <dhowells@...hat.com>, keyrings@...r.kernel.org,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH RESEND] KEYS: fix parsing invalid pkey info string

On Mon, 2018-12-17 at 11:06 -0800, Linus Torvalds wrote:
> On Mon, Dec 17, 2018 at 10:49 AM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > So the *simplest* fix would seem to be to literally remove all those
> > "= -1" for the Opt_err initialization.  Making the code smaller,
> > simpler, and fixing the bug in the process.
> 
> Something like this
> 
>     git  grep -l 'Opt_err = -1' | xargs sed -i 's/Opt_err = -1/Opt_err/'
> 
> would do it, but I also notice that
> security/integrity/ima/ima_policy.c then has some truly funky code
> that plays around with the enum numbers , ie
> 
>   #define pt(token)     policy_tokens[token + Opt_err].pattern

Yikes!

> which actually depends on the ordering of policy_tokens[], and depends
> on the exact values, ie it literally (and quite insanely) sets Opt_err
> to -1, and then Opt_measure to 1, and leaves 0 unused. That code
> seriously makes no sense at all, and is fundamentally broken.
> 
> It would be better to use
> 
>     #define pt(token)     policy_tokens[token - Opt_measure].pattern
> 
> instead, but even then you should have a huge comment about how the
> policy_tokens[] array absolutely has to be properly ordered.

Will do.

> 
> Honestly, for being about "security", all of this code seems to be
> doing some really questionable things with all those Opt_xyz enums.

It's being used for parsing and displaying the policy, which do need
to be in sync.

Mimi