linux-kernel - [PATCH v8 3/4] arm64: kexec_file: use more system keyrings to verify kernel image signature

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Date:   Thu, 12 May 2022 15:01:22 +0800
From:   Coiby Xu <coxu@...hat.com>
To:     kexec@...ts.infradead.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        Michal Suchanek <msuchanek@...e.de>,
        Baoquan He <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
        Will Deacon <will@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Mimi Zohar <zohar@...ux.ibm.com>, Chun-Yi Lee <jlee@...e.com>,
        stable@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v8 3/4] arm64: kexec_file: use more system keyrings to verify kernel image signature

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@...r.kernel.org # 34d5960af253: kexec: clean up arch_kexec_kernel_verify_sig
Cc: stable@...r.kernel.org # 83b7bb2d49ae: kexec, KEYS: make the code in bzImage64_verify_sig generic
Acked-by: Baoquan He <bhe@...hat.com>
Cc: kexec@...ts.infradead.org
Cc: keyrings@...r.kernel.org
Cc: linux-security-module@...r.kernel.org
Co-developed-by: Michal Suchanek <msuchanek@...e.de>
Signed-off-by: Michal Suchanek <msuchanek@...e.de>
Acked-by: Will Deacon <will@...nel.org>
Signed-off-by: Coiby Xu <coxu@...hat.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