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From:   Michal Suchanek <msuchanek@suse.de>
To:     keyrings@vger.kernel.org
Cc:     Michal Suchanek <msuchanek@suse.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
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Subject: [PATCH 3/3] powerpc/kexec_file: Add KEXEC_SIG support.
Date:   Wed,  3 Nov 2021 15:27:08 +0100
Message-Id: <ba7ffddf9e15288baeae6c2099e573509321738c.1635948742.git.msuchanek@suse.de>
In-Reply-To: <cover.1635948742.git.msuchanek@suse.de>
References: <cover.1635948742.git.msuchanek@suse.de>
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Use the module verifier for the kernel image verification.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/Kconfig        | 11 +++++++++++
 arch/powerpc/kexec/elf_64.c | 14 ++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 743c9783c64f..27bffafa9e79 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -558,6 +558,17 @@ config KEXEC_FILE
 config ARCH_HAS_KEXEC_PURGATORY
 	def_bool KEXEC_FILE
 
+config KEXEC_SIG
+	bool "Verify kernel signature during kexec_file_load() syscall"
+	depends on KEXEC_FILE && MODULE_SIG_FORMAT
+	help
+	  This option makes kernel signature verification mandatory for
+	  the kexec_file_load() syscall.
+
+	  In addition to that option, you need to enable signature
+	  verification for the corresponding kernel image type being
+	  loaded in order for this to work.
+
 config PPC64_BUILD_ELF_V2_ABI
 	bool
 
diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
index eeb258002d1e..e8dff6b23ac5 100644
--- a/arch/powerpc/kexec/elf_64.c
+++ b/arch/powerpc/kexec/elf_64.c
@@ -23,6 +23,7 @@
 #include <linux/of_fdt.h>
 #include <linux/slab.h>
 #include <linux/types.h>
+#include <linux/verification.h>
 
 static void *elf64_load(struct kimage *image, char *kernel_buf,
 			unsigned long kernel_len, char *initrd,
@@ -151,7 +152,20 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
 	return ret ? ERR_PTR(ret) : NULL;
 }
 
+#ifdef CONFIG_KEXEC_SIG
+int elf64_verify_sig(const char *kernel, unsigned long length)
+{
+	size_t kernel_len = length;
+
+	return verify_appended_signature(kernel, &kernel_len, VERIFY_USE_PLATFORM_KEYRING,
+					 "kexec_file");
+}
+#endif /* CONFIG_KEXEC_SIG */
+
 const struct kexec_file_ops kexec_elf64_ops = {
 	.probe = kexec_elf_probe,
 	.load = elf64_load,
+#ifdef CONFIG_KEXEC_SIG
+	.verify_sig = elf64_verify_sig,
+#endif
 };
-- 
2.31.1