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

Kees Cook
2019-06-23T00:00:33Z

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

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

-Kees

> Signed-off-by: Matthew Garrett <mjg59@google.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