Re: [PATCH V34 10/29] hibernate: Disable when the kernel is locked down

Kees Cook
2019-06-22T23:55:05Z

On Fri, Jun 21, 2019 at 05:03:39PM -0700, Matthew Garrett wrote:
> From: Josh Boyer <jwboyer@fedoraproject.org>
>
> There is currently no way to verify the resume image when returning
> from hibernate. This might compromise the signed modules trust model,
> so until we can work with signed hibernate images we disable it when the
> kernel is locked down.
>
> Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>

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

-Kees

> Signed-off-by: David Howells <dhowells@redhat.com>
> Signed-off-by: Matthew Garrett <mjg59@google.com>
> Cc: rjw@rjwysocki.net
> Cc: pavel@ucw.cz
> cc: linux-pm@vger.kernel.org
> ---
> include/linux/security.h | 1 +
> kernel/power/hibernate.c | 3 ++-
> security/lockdown/lockdown.c | 1 +
> 3 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 00a31ab2e5ba..a051f21a1144 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -85,6 +85,7 @@ enum lockdown_reason {
> LOCKDOWN_MODULE_SIGNATURE,
> LOCKDOWN_DEV_MEM,
> LOCKDOWN_KEXEC,
> + LOCKDOWN_HIBERNATION,
> LOCKDOWN_INTEGRITY_MAX,
> LOCKDOWN_CONFIDENTIALITY_MAX,
> };
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index abef759de7c8..3a9cb2d3da4a 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -32,6 +32,7 @@
> #include <linux/ctype.h>
> #include <linux/genhd.h>
> #include <linux/ktime.h>
> +#include <linux/security.h>
> #include <trace/events/power.h>
>
> #include "power.h"
> @@ -70,7 +71,7 @@ static const struct platform_hibernation_ops *hibernation_ops;
>
> bool hibernation_available(void)
> {
> - return (nohibernate == 0);
> + return nohibernate == 0 && !security_locked_down(LOCKDOWN_HIBERNATION);
> }
>
> /**
> diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
> index 08fcd8116db3..ce5b3da9bd09 100644
> --- a/security/lockdown/lockdown.c
> +++ b/security/lockdown/lockdown.c
> @@ -21,6 +21,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
> [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading",
> [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
> [LOCKDOWN_KEXEC] = "kexec of unsigned images",
> + [LOCKDOWN_HIBERNATION] = "hibernation",
> [LOCKDOWN_INTEGRITY_MAX] = "integrity",
> [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
> };
> --
> 2.22.0.410.gd8fdbe21b5-goog
>

--
Kees Cook