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

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Message-ID: <20181231224530.GA12425@zzz.localdomain>
Date:   Mon, 31 Dec 2018 16:45:31 -0600
From:   Eric Biggers <ebiggers@...nel.org>
To:     David Howells <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     James Bottomley <James.Bottomley@...senpartnership.com>,
        James Morris <jmorris@...ei.org>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>, 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

Hi David and Linus,

On Mon, Dec 17, 2018 at 12:02:01PM -0800, Linus Torvalds wrote:
> On Mon, Dec 17, 2018 at 11:51 AM James Bottomley
> <James.Bottomley@...senpartnership.com> wrote:
> >
> > If this is to replace Eric's patch, didn't you want to set token_mask
> > to (1<<Opt_err)?
> 
> No, let's not add any extra code that is trying to be subtle. Subtle
> interactions was where the bug came from.
> 
> The code already checks the actual Opt_xyz for errors in a switch
> statement. The token_mask should be _purely_ about duplicate options
> (or conflicting ones).
> 
> Talking about the conflicting ones: Opt_hash checks that
> Opt_policydigest isn't set. But Opt_policydigest doesn't check that
> Opt_hash isn't set, so you can mix the two if you just do it in the
> right order.
> 
> But that's a separate bug, and doesn't seem to be a huge deal.
> 
> But it *is* an example of how bogus all of this stuff is. Clearly
> people weren't really paying attention when writing any of this code.
> 
>                         Linus

KEYCTL_PKEY_QUERY is still failing basic fuzzing even after Linus' fix that
changed Opt_err from -1 to 0.  The crash is still in keyctl_pkey_params_parse():

		token = match_token(p, param_keys, args);
		if (__test_and_set_bit(token, &token_mask))
			return -EINVAL;
		q = args[0].from;
		if (!q[0])
			return -EINVAL;

Now it crashes on '!q[0]' because 'args[0].from' is uninitialized when
token == Opt_err.  args[0] is only initialized when the parsed token had a
pattern that set it.

David, where are the tests for these new keyctls?

- Eric