Re: [PATCH V34 07/29] Copy secure_boot flag in boot params across kexec reboot

Kees Cook
2019-06-22T23:53:23Z

On Fri, Jun 21, 2019 at 05:03:36PM -0700, Matthew Garrett wrote:
> From: Dave Young <dyoung@redhat.com>
>
> Kexec reboot in case secure boot being enabled does not keep the secure
> boot mode in new kernel, so later one can load unsigned kernel via legacy
> kexec_load. In this state, the system is missing the protections provided
> by secure boot.
>
> Adding a patch to fix this by retain the secure_boot flag in original
> kernel.
>
> secure_boot flag in boot_params is set in EFI stub, but kexec bypasses the
> stub. Fixing this issue by copying secure_boot flag across kexec reboot.
>
> Signed-off-by: Dave Young <dyoung@redhat.com>

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: kexec@lists.infradead.org
> ---
> arch/x86/kernel/kexec-bzimage64.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> index 22f60dd26460..4243359ac509 100644
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -182,6 +182,7 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
> if (efi_enabled(EFI_OLD_MEMMAP))
> return 0;
>
> + params->secure_boot = boot_params.secure_boot;
> ei->efi_loader_signature = current_ei->efi_loader_signature;
> ei->efi_systab = current_ei->efi_systab;
> ei->efi_systab_hi = current_ei->efi_systab_hi;
> --
> 2.22.0.410.gd8fdbe21b5-goog
>

--
Kees Cook