Merge remote-tracking branch 'linux-integrity/kexec-keyrings' into next-integrity

From the cover letter:

Currently when loading a kernel image via the kexec_file_load() system
call, x86 can make use of three keyrings i.e. the .builtin_trusted_keys,
.secondary_trusted_keys and .platform keyrings to verify a signature.
However, arm64 and s390 can only use the .builtin_trusted_keys and
.platform keyring respectively. For example, one resulting problem is
kexec'ing a kernel image  would be rejected with the error "Lockdown:
kexec: kexec of unsigned images is restricted; see man
kernel_lockdown.7".

This patch set enables arm64 and s390 to make use of the same keyrings
as x86 to verify the signature kexec'ed kernel image.

The recently introduced .machine keyring impacts the roots of trust by
linking the .machine keyring to the .secondary keyring. The roots of
trust for different keyrings are described as follows,

.builtin_trusted_keys:

Keys may be built into the kernel during build or inserted into memory
reserved for keys post build. The root of trust is based on verification
of the kernel image signature. For example, on a physical system in a
secure boot environment, this trust is rooted in hardware.

.machine:

If the end-users choose to trust the keys provided by first-stage UEFI
bootloader shim i.e. Machine Owner Keys (MOK keys), the keys will be
added to this keyring which is linked to the .secondary_trusted_keys
keyring as the same as the .builtin_trusted_keys keyring. Shim has
built-in keys from a Linux distribution or the end-users-enrolled keys.
So the root of trust of this keyring is either a Linux distribution
vendor or the end-users.

.secondary_trusted_keys:

Certificates signed by keys on the .builtin_trusted_keys, .machine, or
existing keys on the .secondary_trusted_keys keryings may be loaded
onto the .secondary_trusted_keys keyring. This establishes a signature
chain of trust based on keys loaded on either the .builtin_trusted_keys
or .machine keyrings, if configured and enabled.

.platform:

The .platform keyring consist of UEFI db and MOK keys which are used by
shim to verify the first boot kernel's image signature. If end-users
choose to trust MOK keys and the kernel has the .machine keyring
enabled, the .platform keyring only consists of UEFI db keys since the
MOK keys are added to the .machine keyring instead. Because the
end-users could also enroll their own MOK keys, the root of trust could
be hardware and the end-users.

2 files changed, 31 insertions, 79 deletions

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 4d34c78334ce..acd029b307e4 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -591,11 +591,6 @@ static void kimage_free_extra_pages(struct kimage *image)
 
 }
 
-int __weak machine_kexec_post_load(struct kimage *image)
-{
-	return 0;
-}
-
 void kimage_terminate(struct kimage *image)
 {
 	if (*image->entry != 0)
@@ -1020,15 +1015,6 @@ size_t crash_get_memory_size(void)
 	return size;
 }
 
-void __weak crash_free_reserved_phys_range(unsigned long begin,
-					   unsigned long end)
-{
-	unsigned long addr;
-
-	for (addr = begin; addr < end; addr += PAGE_SIZE)
-		free_reserved_page(boot_pfn_to_page(addr >> PAGE_SHIFT));
-}
-
 int crash_shrink_memory(unsigned long new_size)
 {
 	int ret = 0;
@@ -1225,16 +1211,3 @@ int kernel_kexec(void)
 	mutex_unlock(&kexec_mutex);
 	return error;
 }
-
-/*
- * Protection mechanism for crashkernel reserved memory after
- * the kdump kernel is loaded.
- *
- * Provide an empty default implementation here -- architecture
- * code may override this
- */
-void __weak arch_kexec_protect_crashkres(void)
-{}
-
-void __weak arch_kexec_unprotect_crashkres(void)
-{}
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f9261c07b048..a7b411c22f19 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -62,14 +62,7 @@ int kexec_image_probe_default(struct kimage *image, void *buf,
 	return ret;
 }
 
-/* Architectures can provide this probe function */
-int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
-					 unsigned long buf_len)
-{
-	return kexec_image_probe_default(image, buf, buf_len);
-}
-
-static void *kexec_image_load_default(struct kimage *image)
+void *kexec_image_load_default(struct kimage *image)
 {
 	if (!image->fops || !image->fops->load)
 		return ERR_PTR(-ENOEXEC);
@@ -80,11 +73,6 @@ static void *kexec_image_load_default(struct kimage *image)
 				 image->cmdline_buf_len);
 }
 
-void * __weak arch_kexec_kernel_image_load(struct kimage *image)
-{
-	return kexec_image_load_default(image);
-}
-
 int kexec_image_post_load_cleanup_default(struct kimage *image)
 {
 	if (!image->fops || !image->fops->cleanup)
@@ -93,30 +81,6 @@ int kexec_image_post_load_cleanup_default(struct kimage *image)
 	return image->fops->cleanup(image->image_loader_data);
 }
 
-int __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
-{
-	return kexec_image_post_load_cleanup_default(image);
-}
-
-#ifdef CONFIG_KEXEC_SIG
-static int kexec_image_verify_sig_default(struct kimage *image, void *buf,
-					  unsigned long buf_len)
-{
-	if (!image->fops || !image->fops->verify_sig) {
-		pr_debug("kernel loader does not support signature verification.\n");
-		return -EKEYREJECTED;
-	}
-
-	return image->fops->verify_sig(buf, buf_len);
-}
-
-int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
-					unsigned long buf_len)
-{
-	return kexec_image_verify_sig_default(image, buf, buf_len);
-}
-#endif
-
 /*
  * Free up memory used by kernel, initrd, and command line. This is temporary
  * memory allocation which is not needed any more after these buffers have
@@ -159,13 +123,41 @@ void kimage_file_post_load_cleanup(struct kimage *image)
 }
 
 #ifdef CONFIG_KEXEC_SIG
+#ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
+int kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len)
+{
+	int ret;
+
+	ret = verify_pefile_signature(kernel, kernel_len,
+				      VERIFY_USE_SECONDARY_KEYRING,
+				      VERIFYING_KEXEC_PE_SIGNATURE);
+	if (ret == -ENOKEY && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING)) {
+		ret = verify_pefile_signature(kernel, kernel_len,
+					      VERIFY_USE_PLATFORM_KEYRING,
+					      VERIFYING_KEXEC_PE_SIGNATURE);
+	}
+	return ret;
+}
+#endif
+
+static int kexec_image_verify_sig(struct kimage *image, void *buf,
+				  unsigned long buf_len)
+{
+	if (!image->fops || !image->fops->verify_sig) {
+		pr_debug("kernel loader does not support signature verification.\n");
+		return -EKEYREJECTED;
+	}
+
+	return image->fops->verify_sig(buf, buf_len);
+}
+
 static int
 kimage_validate_signature(struct kimage *image)
 {
 	int ret;
 
-	ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
-					   image->kernel_buf_len);
+	ret = kexec_image_verify_sig(image, image->kernel_buf,
+				     image->kernel_buf_len);
 	if (ret) {
 
 		if (sig_enforce) {
@@ -622,19 +614,6 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf)
 }
 
 /**
- * arch_kexec_locate_mem_hole - Find free memory to place the segments.
- * @kbuf:                       Parameters for the memory search.
- *
- * On success, kbuf->mem will have the start address of the memory region found.
- *
- * Return: 0 on success, negative errno on error.
- */
-int __weak arch_kexec_locate_mem_hole(struct kexec_buf *kbuf)
-{
-	return kexec_locate_mem_hole(kbuf);
-}
-
-/**
  * kexec_add_buffer - place a buffer in a kexec segment
  * @kbuf:	Buffer contents and memory parameters.
  *