[PATCH v7 3/4] arm64: kexec_file: use more system keyrings to verify kernel image signature

Coiby Xu
2022-05-12T02:34:25Z

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 happens 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_keys
keyring.

Fixes: 732b7b93d849 ("arm64: kexec_file: add kernel signature verification support")
Cc: stable@vger.kernel.org # 34d5960af253: kexec: clean up arch_kexec_kernel_verify_sig
Cc: stable@vger.kernel.org # 83b7bb2d49ae: kexec, KEYS: make the code in bzImage64_verify_sig generic
Acked-by: Baoquan He <bhe@redhat.com>
Cc: kexec@lists.infradead.org
Cc: keyrings@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Co-developed-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
arch/arm64/kernel/kexec_image.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
index 9ec34690e255..5ed6a585f21f 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>
@@ -130,18 +129,10 @@ static void *image_load(struct kimage *image,
return NULL;
}

-#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);
-}
-#endif
-
const struct kexec_file_ops kexec_image_ops = {
.probe = image_probe,
.load = image_load,
#ifdef CONFIG_KEXEC_IMAGE_VERIFY_SIG
- .verify_sig = image_verify_sig,
+ .verify_sig = kexec_kernel_verify_pe_sig,
#endif
};
--
2.35.3