linux-kernel - Re: [PATCH RFC v10 5/17] ipe: introduce 'boot

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Date:   Sat, 08 Jul 2023 01:36:57 -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,
        Deven Bowers <deven.desai@...ux.microsoft.com>,
        Fan Wu <wufan@...ux.microsoft.com>
Subject: Re: [PATCH RFC v10 5/17] ipe: introduce 'boot_verified' as a trust  provider

On Jun 28, 2023 Fan Wu <wufan@...ux.microsoft.com> wrote:
> 
> IPE is designed to provide system level trust guarantees, this usually
> implies that trust starts from bootup with a hardware root of trust,
> which validates the bootloader. After this, the bootloader verifies the
> kernel and the initramfs.
> 
> As there's no currently supported integrity method for initramfs, and
> it's typically already verified by the bootloader, introduce a property
> that causes the first superblock to have an execution to be "pinned",
> which is typically initramfs.
> 
> When the "pinned" device is unmounted, it will be "unpinned" and
> `boot_verified` property will always evaluate to false afterward.
> 
> We use a pointer with a spin_lock to "pin" the device instead of rcu
> because rcu synchronization may sleep, which is not allowed when
> unmounting a device.
> 
> Signed-off-by: Deven Bowers <deven.desai@...ux.microsoft.com>
> Signed-off-by: Fan Wu <wufan@...ux.microsoft.com>
> ---
>  security/ipe/eval.c          | 72 +++++++++++++++++++++++++++++++++++-
>  security/ipe/eval.h          |  2 +
>  security/ipe/hooks.c         | 12 ++++++
>  security/ipe/hooks.h         |  2 +
>  security/ipe/ipe.c           |  1 +
>  security/ipe/policy.h        |  2 +
>  security/ipe/policy_parser.c | 37 +++++++++++++++++-
>  7 files changed, 126 insertions(+), 2 deletions(-)

The compilation errors continue into this patch.

> diff --git a/security/ipe/policy_parser.c b/security/ipe/policy_parser.c
> index 27e5767480b0..28c14adfe6d2 100644
> --- a/security/ipe/policy_parser.c
> +++ b/security/ipe/policy_parser.c
> @@ -265,6 +265,12 @@ static enum ipe_action_type parse_action(char *t)
>  	return match_token(t, action_tokens, args);
>  }
>  
> +static const match_table_t property_tokens = {
> +	{__IPE_PROP_BOOT_VERIFIED_FALSE,	"boot_verified=FALSE"},
> +	{__IPE_PROP_BOOT_VERIFIED_TRUE,		"boot_verified=TRUE"},
> +	{__IPE_PROP_INVALID,			NULL}
> +};
> +
>  /**
>   * parse_property - Parse the property type given a token string.
>   * @t: Supplies the token string to be parsed.
> @@ -277,7 +283,36 @@ static enum ipe_action_type parse_action(char *t)
>   */
>  static int parse_property(char *t, struct ipe_rule *r)
>  {
> -	return -EBADMSG;
> +	substring_t args[MAX_OPT_ARGS];
> +	struct ipe_prop *p = NULL;
> +	int rc = 0;
> +	int token;
> +
> +	p = kzalloc(sizeof(*p), GFP_KERNEL);
> +	if (!p)
> +		return -ENOMEM;
> +
> +	token = match_token(t, property_tokens, args);
> +
> +	switch (token) {
> +	case __IPE_PROP_BOOT_VERIFIED_FALSE:
> +	case __IPE_PROP_BOOT_VERIFIED_TRUE:
> +		p->type = token;
> +		break;
> +	case __IPE_PROP_INVALID:

You generally don't need to explicitly specify a case if the code
immediately falls through to 'default'.

> +	default:
> +		rc = -EBADMSG;
> +		break;
> +	}
> +	if (rc)
> +		goto err;
> +	list_add_tail(&p->next, &r->props);
> +
> +out:
> +	return rc;
> +err:
> +	kfree(p);
> +	goto out;

Once again, don't use a goto when the jump destination simply does a
return, do the return directly.

>  }
>  
>  /**
> -- 
> 2.25.1

--
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