linux-kernel - Re: [PATCH V34 17/29] Prohibit PCMCIA CIS storage when the kernel is locked down

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Message-ID: <201906221700.51ABA736@keescook>
Date:   Sat, 22 Jun 2019 17:00:28 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matthew Garrett <matthewgarrett@...gle.com>
Cc:     jmorris@...ei.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Matthew Garrett <mjg59@...gle.com>
Subject: Re: [PATCH V34 17/29] Prohibit PCMCIA CIS storage when the kernel is
 locked down

On Fri, Jun 21, 2019 at 05:03:46PM -0700, Matthew Garrett wrote:
> From: David Howells <dhowells@...hat.com>
> 
> Prohibit replacement of the PCMCIA Card Information Structure when the
> kernel is locked down.
> 
> Suggested-by: Dominik Brodowski <linux@...inikbrodowski.net>
> Signed-off-by: David Howells <dhowells@...hat.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> Signed-off-by: Matthew Garrett <mjg59@...gle.com>
> ---
>  drivers/pcmcia/cistpl.c      | 5 +++++
>  include/linux/security.h     | 1 +
>  security/lockdown/lockdown.c | 1 +
>  3 files changed, 7 insertions(+)
> 
> diff --git a/drivers/pcmcia/cistpl.c b/drivers/pcmcia/cistpl.c
> index ac0672b8dfca..379c53610102 100644
> --- a/drivers/pcmcia/cistpl.c
> +++ b/drivers/pcmcia/cistpl.c
> @@ -24,6 +24,7 @@
>  #include <linux/pci.h>
>  #include <linux/ioport.h>
>  #include <linux/io.h>
> +#include <linux/security.h>
>  #include <asm/byteorder.h>
>  #include <asm/unaligned.h>
>  
> @@ -1578,6 +1579,10 @@ static ssize_t pccard_store_cis(struct file *filp, struct kobject *kobj,
>  	struct pcmcia_socket *s;
>  	int error;
>  
> +	error = security_locked_down(LOCKDOWN_PCMCIA_CIS);
> +	if (error)
> +		return error;
> +
>  	s = to_socket(container_of(kobj, struct device, kobj));
>  
>  	if (off)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index cc2b5ee4cadd..03c125b277ca 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -90,6 +90,7 @@ enum lockdown_reason {
>  	LOCKDOWN_IOPORT,
>  	LOCKDOWN_MSR,
>  	LOCKDOWN_ACPI_TABLES,
> +	LOCKDOWN_PCMCIA_CIS,
>  	LOCKDOWN_INTEGRITY_MAX,
>  	LOCKDOWN_CONFIDENTIALITY_MAX,
>  };
> diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
> index 1725224f0024..7be3e8fb5847 100644
> --- a/security/lockdown/lockdown.c
> +++ b/security/lockdown/lockdown.c
> @@ -26,6 +26,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
>  	[LOCKDOWN_IOPORT] = "raw io port access",
>  	[LOCKDOWN_MSR] = "raw MSR access",
>  	[LOCKDOWN_ACPI_TABLES] = "modified ACPI tables",
> +	[LOCKDOWN_PCMCIA_CIS] = "direct PCMCIA CIS storage",
>  	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
>  	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
>  };
> -- 
> 2.22.0.410.gd8fdbe21b5-goog
> 

-- 
Kees Cook