Re: [PATCH V34 09/29] kexec_file: Restrict at runtime if the kernel is locked down

[Kees Cook]

On Fri, Jun 21, 2019 at 05:03:38PM -0700, Matthew Garrett wrote:
> From: Jiri Bohac <jbohac@xxxxxxx>
> 
> When KEXEC_SIG is not enabled, kernel should not load images through
> kexec_file systemcall if the kernel is locked down.
> 
> [Modified by David Howells to fit with modifications to the previous patch
>  and to return -EPERM if the kernel is locked down for consistency with
>  other lockdowns. Modified by Matthew Garrett to remove the IMA
>  integration, which will be replaced by integrating with the IMA
>  architecture policy patches.]
> 
> Signed-off-by: Jiri Bohac <jbohac@xxxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> Signed-off-by: Matthew Garrett <mjg59@xxxxxxxxxx>
> Reviewed-by: Jiri Bohac <jbohac@xxxxxxx>
> cc: kexec@xxxxxxxxxxxxxxxxxxx
> ---
>  kernel/kexec_file.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index eec7e5bb2a08..27adb4312b03 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -237,7 +237,10 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
>  			goto out;
>  		}
>  
> -		ret = 0;
> +		ret = security_locked_down(LOCKDOWN_KEXEC);
> +		if (ret)
> +			goto out;
> +
>  		break;
>  
>  		/* All other errors are fatal, including nomem, unparseable
> -- 
> 2.22.0.410.gd8fdbe21b5-goog
> 

-- 
Kees Cook