x86/kexec: Carry forward IMA measurement log on kexec

On kexec file load, the Integrity Measurement Architecture (IMA)
subsystem may verify the IMA signature of the kernel and initramfs, and
measure it. The command line parameters passed to the kernel in the
kexec call may also be measured by IMA.

A remote attestation service can verify a TPM quote based on the TPM
event log, the IMA measurement list and the TPM PCR data. This can
be achieved only if the IMA measurement log is carried over from the
current kernel to the next kernel across the kexec call.

PowerPC and ARM64 both achieve this using device tree with a
"linux,ima-kexec-buffer" node. x86 platforms generally don't make use of
device tree, so use the setup_data mechanism to pass the IMA buffer to
the new kernel.

Signed-off-by: Jonathan McDowell <noodles@fb.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> # IMA function definitions
Link: https://lore.kernel.org/r/YmKyvlF3my1yWTvK@noodles-fedora-PC23Y6EG

1 files changed, 40 insertions, 2 deletions

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 170d0fd68b1f..c63974e94272 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -186,11 +186,38 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
 }
 #endif /* CONFIG_EFI */
 
+static void
+setup_ima_state(const struct kimage *image, struct boot_params *params,
+		unsigned long params_load_addr,
+		unsigned int ima_setup_data_offset)
+{
+#ifdef CONFIG_IMA_KEXEC
+	struct setup_data *sd = (void *)params + ima_setup_data_offset;
+	unsigned long setup_data_phys;
+	struct ima_setup_data *ima;
+
+	if (!image->ima_buffer_size)
+		return;
+
+	sd->type = SETUP_IMA;
+	sd->len = sizeof(*ima);
+
+	ima = (void *)sd + sizeof(struct setup_data);
+	ima->addr = image->ima_buffer_addr;
+	ima->size = image->ima_buffer_size;
+
+	/* Add setup data */
+	setup_data_phys = params_load_addr + ima_setup_data_offset;
+	sd->next = params->hdr.setup_data;
+	params->hdr.setup_data = setup_data_phys;
+#endif /* CONFIG_IMA_KEXEC */
+}
+
 static int
 setup_boot_parameters(struct kimage *image, struct boot_params *params,
 		      unsigned long params_load_addr,
 		      unsigned int efi_map_offset, unsigned int efi_map_sz,
-		      unsigned int efi_setup_data_offset)
+		      unsigned int setup_data_offset)
 {
 	unsigned int nr_e820_entries;
 	unsigned long long mem_k, start, end;
@@ -245,8 +272,15 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
 #ifdef CONFIG_EFI
 	/* Setup EFI state */
 	setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
-			efi_setup_data_offset);
+			setup_data_offset);
+	setup_data_offset += sizeof(struct setup_data) +
+			sizeof(struct efi_setup_data);
 #endif
+
+	/* Setup IMA log buffer state */
+	setup_ima_state(image, params, params_load_addr,
+			setup_data_offset);
+
 	/* Setup EDD info */
 	memcpy(params->eddbuf, boot_params.eddbuf,
 				EDDMAXNR * sizeof(struct edd_info));
@@ -403,6 +437,10 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 				sizeof(struct setup_data) +
 				sizeof(struct efi_setup_data);
 
+	if (IS_ENABLED(CONFIG_IMA_KEXEC))
+		kbuf.bufsz += sizeof(struct setup_data) +
+			      sizeof(struct ima_setup_data);
+
 	params = kzalloc(kbuf.bufsz, GFP_KERNEL);
 	if (!params)
 		return ERR_PTR(-ENOMEM);