Re: [PATCH v5 3/3] arm64: kexec_file: use more system keyrings to verify kernel image signature

[Coiby Xu]

On Mon, Apr 11, 2022 at 10:59:38AM +0200, Michal Suchánek wrote:
> On Fri, Apr 01, 2022 at 09:31:18AM +0800, Coiby Xu wrote:
> > Currently, a problem faced by arm64 is if a kernel image is signed by a
> > MOK key, loading it via the kexec_file_load() system call would be
> > rejected with the error "Lockdown: kexec: kexec of unsigned images is
> > restricted; see man kernel_lockdown.7".
>
> This is because image_verify_sig uses only the primary keyring that
> contains only kernel built-in keys to verify the kexec image.
>
> > This patch allows to verify arm64 kernel image signature using not only
> > .builtin_trusted_keys but also .platform and .secondary_trusted_key
> > keyring.
> >
> > Acked-by: Will Deacon <will@xxxxxxxxxx>
> > Signed-off-by: Coiby Xu <coxu@xxxxxxxxxx>
> > ---
> >  arch/arm64/kernel/kexec_image.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
> > index 9ec34690e255..51af1c22d6da 100644
> > --- a/arch/arm64/kernel/kexec_image.c
> > +++ b/arch/arm64/kernel/kexec_image.c
> > @@ -14,7 +14,6 @@
> >  #include <linux/kexec.h>
> >  #include <linux/pe.h>
> >  #include <linux/string.h>
> > -#include <linux/verification.h>
> >  #include <asm/byteorder.h>
> >  #include <asm/cpufeature.h>
> >  #include <asm/image.h>
> > @@ -133,8 +132,7 @@ static void *image_load(struct kimage *image,
> >  #ifdef CONFIG_KEXEC_IMAGE_VERIFY_SIG
> >  static int image_verify_sig(const char *kernel, unsigned long kernel_len)
> >  {
> > -	return verify_pefile_signature(kernel, kernel_len, NULL,
> > -				       VERIFYING_KEXEC_PE_SIGNATURE);
> > +	return kexec_kernel_verify_pe_sig(kernel, kernel_len);
> >  }
> >  #endif
>
> You can eliminate image_verify_sig here aswell and directly assign
> kexec_kernel_verify_pe_sig to fops.

Good suggestions, thanks!

> Thanks
>
> Michal

--
Best regards,
Coiby