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[PATCHC v7 00/10] ima: carry the measurement list across kexec

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  [PATCHC v7 00/10] ima: carry the measurement list across kexec Mimi Zohar <zohar@linux.vnet.ibm.com> - 2016-11-10 16:00 +0100
    [PATCHC v7 02/10] ima: on soft reboot, restore the measurement list Mimi Zohar <zohar@linux.vnet.ibm.com> - 2016-11-10 16:00 +0100
    [PATCHC v7 01/10] powerpc: ima: Get the kexec buffer passed by the previous kernel Mimi Zohar <zohar@linux.vnet.ibm.com> - 2016-11-10 16:00 +0100

#1519036 — [PATCHC v7 00/10] ima: carry the measurement list across kexec

[Posting with abbreviated Cc list.]

The TPM PCRs are only reset on a hard reboot.  In order to validate a
TPM's quote after a soft reboot (eg. kexec -e), the IMA measurement list
of the running kernel must be saved and then restored on the subsequent
boot, possibly of a different architecture.

The existing securityfs binary_runtime_measurements file conveniently
provides a serialized format of the IMA measurement list. This patch
set serializes the measurement list in this format and restores it.

Up to now, the binary_runtime_measurements was defined as architecture
native format.  The assumption being that userspace could and would
handle any architecture conversions.  With the ability of carrying the
measurement list across kexec, possibly from one architecture to a
different one, the per boot architecture information is lost and with it
the ability of recalculating the template digest hash.  To resolve this
problem, without breaking the existing ABI, this patch set introduces
the boot command line option "ima_canonical_fmt", which is arbitrarily
defined as little endian.

The need for this boot command line option will be limited to the
existing version 1 format of the binary_runtime_measurements.
Subsequent formats will be defined as canonical format (eg. TPM 2.0
support for larger digests).

A simplified method of Thiago Bauermann's "kexec buffer handover" patch
series for carrying the IMA measurement list across kexec is included
in this patch set.  The simplified method requires all file measurements
be taken prior to executing the kexec load, as subsequent measurements
will not be carried across the kexec and restored.

These patches can also be found in the next-kexec-restore branch of:
git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git

Changelog v7:
- Updated to reflect Dmitry Kasatkin's patch review
- Rebased on top of "next-fixes" branch

Andreas Steffen (1):
  ima: platform-independent hash value

Mimi Zohar (7):
  ima: on soft reboot, restore the measurement list
  ima: permit duplicate measurement list entries
  ima: maintain memory size needed for serializing the measurement list
  ima: on soft reboot, save the measurement list
  ima: store the builtin/custom template definitions in a list
  ima: support restoring multiple template formats
  ima: define a canonical binary_runtime_measurements list format

Thiago Jung Bauermann (2):
  powerpc: ima: Get the kexec buffer passed by the previous kernel
  powerpc: ima: Send the kexec buffer to the next kernel

 Documentation/kernel-parameters.txt         |   4 +
 arch/Kconfig                                |   3 +
 arch/powerpc/Kconfig                        |   1 +
 arch/powerpc/include/asm/ima.h              |  29 +++
 arch/powerpc/include/asm/kexec.h            |  15 +-
 arch/powerpc/kernel/Makefile                |   4 +
 arch/powerpc/kernel/ima_kexec.c             | 223 +++++++++++++++++++++
 arch/powerpc/kernel/kexec_elf_64.c          |   2 +-
 arch/powerpc/kernel/machine_kexec_file_64.c |  15 +-
 include/linux/ima.h                         |  12 ++
 kernel/kexec_file.c                         |   4 +
 security/integrity/ima/Kconfig              |  12 ++
 security/integrity/ima/Makefile             |   1 +
 security/integrity/ima/ima.h                |  31 +++
 security/integrity/ima/ima_crypto.c         |   6 +-
 security/integrity/ima/ima_fs.c             |  30 ++-
 security/integrity/ima/ima_init.c           |   2 +
 security/integrity/ima/ima_kexec.c          | 168 ++++++++++++++++
 security/integrity/ima/ima_main.c           |   1 +
 security/integrity/ima/ima_queue.c          |  77 +++++++-
 security/integrity/ima/ima_template.c       | 297 ++++++++++++++++++++++++++--
 security/integrity/ima/ima_template_lib.c   |   7 +-
 22 files changed, 906 insertions(+), 38 deletions(-)
 create mode 100644 arch/powerpc/include/asm/ima.h
 create mode 100644 arch/powerpc/kernel/ima_kexec.c
 create mode 100644 security/integrity/ima/ima_kexec.c

-- 
2.1.0

[toc] | [next] | [standalone]

#1519037 — [PATCHC v7 02/10] ima: on soft reboot, restore the measurement list

The TPM PCRs are only reset on a hard reboot.  In order to validate a
TPM's quote after a soft reboot (eg. kexec -e), the IMA measurement list
of the running kernel must be saved and restored on boot.  This patch
restores the measurement list.

Changelog v7:
- add and fix missing buffer length checking (reported by D. Kasatkin)
- clean up ima_restore_measurement_list() a bit

Changelog v5:
- replace CONFIG_KEXEC_FILE with architecture CONFIG_HAVE_IMA_KEXEC (Thiago)
- replace kexec_get_handover_buffer() with ima_get_kexec_buffer() (Thiago)
- replace kexec_free_handover_buffer() with ima_free_kexec_buffer() (Thiago)
- remove unnecessary includes from ima_kexec.c (Thiago)
- fix off-by-one error when checking hdr_v1->template_name_len (Colin King)

Changelog v2:
- redefined ima_kexec_hdr to use types with well defined sizes (M. Ellerman)
- defined missing ima_load_kexec_buffer() stub function

Changelog v1:
- call ima_load_kexec_buffer() (Thiago)

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 security/integrity/ima/Makefile       |   1 +
 security/integrity/ima/ima.h          |  21 ++++
 security/integrity/ima/ima_init.c     |   2 +
 security/integrity/ima/ima_kexec.c    |  44 +++++++++
 security/integrity/ima/ima_queue.c    |  10 ++
 security/integrity/ima/ima_template.c | 177 ++++++++++++++++++++++++++++++++++
 6 files changed, 255 insertions(+)
 create mode 100644 security/integrity/ima/ima_kexec.c

diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 9aeaedad1e2b..29f198bde02b 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -8,4 +8,5 @@ obj-$(CONFIG_IMA) += ima.o
 ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
 	 ima_policy.o ima_template.o ima_template_lib.o
 ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
+ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index db25f54a04fe..51dc8d57d64d 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -28,6 +28,10 @@
 
 #include "../integrity.h"
 
+#ifdef CONFIG_HAVE_IMA_KEXEC
+#include <asm/ima.h>
+#endif
+
 enum ima_show_type { IMA_SHOW_BINARY, IMA_SHOW_BINARY_NO_FIELD_LEN,
 		     IMA_SHOW_BINARY_OLD_STRING_FMT, IMA_SHOW_ASCII };
 enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8 };
@@ -102,6 +106,21 @@ struct ima_queue_entry {
 };
 extern struct list_head ima_measurements;	/* list of all measurements */
 
+/* Some details preceding the binary serialized measurement list */
+struct ima_kexec_hdr {
+	u16 version;
+	u16 _reserved0;
+	u32 _reserved1;
+	u64 buffer_size;
+	u64 count;
+};
+
+#ifdef CONFIG_HAVE_IMA_KEXEC
+void ima_load_kexec_buffer(void);
+#else
+static inline void ima_load_kexec_buffer(void) {}
+#endif /* CONFIG_HAVE_IMA_KEXEC */
+
 /* Internal IMA function definitions */
 int ima_init(void);
 int ima_fs_init(void);
@@ -122,6 +141,8 @@ int ima_init_crypto(void);
 void ima_putc(struct seq_file *m, void *data, int datalen);
 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size);
 struct ima_template_desc *ima_template_desc_current(void);
+int ima_restore_measurement_entry(struct ima_template_entry *entry);
+int ima_restore_measurement_list(loff_t bufsize, void *buf);
 int ima_init_template(void);
 
 /*
diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
index 2ac1f41db5c0..2967d497a665 100644
--- a/security/integrity/ima/ima_init.c
+++ b/security/integrity/ima/ima_init.c
@@ -129,6 +129,8 @@ int __init ima_init(void)
 	if (rc != 0)
 		return rc;
 
+	ima_load_kexec_buffer();
+
 	rc = ima_add_boot_aggregate();	/* boot aggregate must be first entry */
 	if (rc != 0)
 		return rc;
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
new file mode 100644
index 000000000000..36afd0fe9747
--- /dev/null
+++ b/security/integrity/ima/ima_kexec.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2016 IBM Corporation
+ *
+ * Authors:
+ * Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
+ * Mimi Zohar <zohar@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+#include "ima.h"
+
+/*
+ * Restore the measurement list from the previous kernel.
+ */
+void ima_load_kexec_buffer(void)
+{
+	void *kexec_buffer = NULL;
+	size_t kexec_buffer_size = 0;
+	int rc;
+
+	rc = ima_get_kexec_buffer(&kexec_buffer, &kexec_buffer_size);
+	switch (rc) {
+	case 0:
+		rc = ima_restore_measurement_list(kexec_buffer_size,
+						  kexec_buffer);
+		if (rc != 0)
+			pr_err("Failed to restore the measurement list: %d\n",
+				rc);
+
+		ima_free_kexec_buffer();
+		break;
+	case -ENOTSUPP:
+		pr_debug("Restoring the measurement list not supported\n");
+		break;
+	case -ENOENT:
+		pr_debug("No measurement list to restore\n");
+		break;
+	default:
+		pr_debug("Error restoring the measurement list: %d\n", rc);
+	}
+}
diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
index 32f6ac0f96df..4b1bb7787839 100644
--- a/security/integrity/ima/ima_queue.c
+++ b/security/integrity/ima/ima_queue.c
@@ -149,3 +149,13 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
 			    op, audit_cause, result, audit_info);
 	return result;
 }
+
+int ima_restore_measurement_entry(struct ima_template_entry *entry)
+{
+	int result = 0;
+
+	mutex_lock(&ima_extend_list_mutex);
+	result = ima_add_digest_entry(entry);
+	mutex_unlock(&ima_extend_list_mutex);
+	return result;
+}
diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index febd12ed9b55..7556a61db483 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -37,6 +37,7 @@ static struct ima_template_field supported_fields[] = {
 	{.field_id = "sig", .field_init = ima_eventsig_init,
 	 .field_show = ima_show_template_sig},
 };
+#define MAX_TEMPLATE_NAME_LEN 15
 
 static struct ima_template_desc *ima_template;
 static struct ima_template_desc *lookup_template_desc(const char *name);
@@ -205,3 +206,179 @@ int __init ima_init_template(void)
 
 	return result;
 }
+
+static int ima_restore_template_data(struct ima_template_desc *template_desc,
+				     void *template_data,
+				     int template_data_size,
+				     struct ima_template_entry **entry)
+{
+	struct binary_field_data {
+		u32 len;
+		u8 data[0];
+	} __packed;
+
+	struct binary_field_data *field_data;
+	int offset = 0;
+	int ret = 0;
+	int i;
+
+	*entry = kzalloc(sizeof(**entry) +
+		    template_desc->num_fields * sizeof(struct ima_field_data),
+		    GFP_NOFS);
+	if (!*entry)
+		return -ENOMEM;
+
+	(*entry)->template_desc = template_desc;
+	for (i = 0; i < template_desc->num_fields; i++) {
+		field_data = template_data + offset;
+
+		/* Each field of the template data is prefixed with a length. */
+		if (offset > (template_data_size - sizeof(field_data->len))) {
+			pr_err("Restoring the template field failed\n");
+			ret = -EINVAL;
+			break;
+		}
+		offset += sizeof(field_data->len);
+
+		if (offset > (template_data_size - field_data->len)) {
+			pr_err("Restoring the template field data failed\n");
+			ret = -EINVAL;
+			break;
+		}
+		offset += field_data->len;
+
+		(*entry)->template_data[i].len = field_data->len;
+		(*entry)->template_data_len += sizeof(field_data->len);
+
+		(*entry)->template_data[i].data =
+			kzalloc(field_data->len + 1, GFP_KERNEL);
+		if (!(*entry)->template_data[i].data) {
+			ret = -ENOMEM;
+			break;
+		}
+		memcpy((*entry)->template_data[i].data, field_data->data,
+			field_data->len);
+		(*entry)->template_data_len += field_data->len;
+	}
+
+	if (ret < 0) {
+		ima_free_template_entry(*entry);
+		*entry = NULL;
+	}
+
+	return ret;
+}
+
+/* Restore the serialized binary measurement list without extending PCRs. */
+int ima_restore_measurement_list(loff_t size, void *buf)
+{
+	struct binary_hdr_v1 {
+		u32 pcr;
+		u8 digest[TPM_DIGEST_SIZE];
+		u32 template_name_len;
+		char template_name[0];
+	} __packed;
+	char template_name[MAX_TEMPLATE_NAME_LEN];
+
+	struct binary_data_v1 {
+		u32 template_data_size;
+		char template_data[0];
+	} __packed;
+
+	struct ima_kexec_hdr *khdr = buf;
+	struct binary_hdr_v1 *hdr_v1;
+	struct binary_data_v1 *data_v1;
+
+	void *bufp = buf + sizeof(*khdr);
+	void *bufendp = buf + khdr->buffer_size;
+	struct ima_template_entry *entry;
+	struct ima_template_desc *template_desc;
+	unsigned long count = 0;
+	int ret = 0;
+
+	if (!buf || size < sizeof(*khdr))
+		return 0;
+
+	if (khdr->version != 1) {
+		pr_err("attempting to restore a incompatible measurement list");
+		return -EINVAL;
+	}
+
+	if (khdr->count > ULONG_MAX - 1) {
+		pr_err("attempting to restore too many measurements");
+		return -EINVAL;
+	}
+
+	/*
+	 * ima kexec buffer prefix: version, buffer size, count
+	 * v1 format: pcr, digest, template-name-len, template-name,
+	 *	      template-data-size, template-data
+	 */
+	while ((bufp < bufendp) && (count++ < khdr->count)) {
+		hdr_v1 = bufp;
+		if (bufp > (bufendp - sizeof(*hdr_v1))) {
+			pr_err("attempting to restore partial measurement\n");
+			ret = -EINVAL;
+			break;
+		}
+		bufp += sizeof(*hdr_v1);
+
+		if ((hdr_v1->template_name_len >= MAX_TEMPLATE_NAME_LEN) ||
+		    (bufp > (bufendp - hdr_v1->template_name_len))) {
+			pr_err("attempting to restore a template name \
+				that is too long\n");
+			ret = -EINVAL;
+			break;
+		}
+		data_v1 = bufp += (u_int8_t)hdr_v1->template_name_len;
+
+		/* template name is not null terminated */
+		memcpy(template_name, hdr_v1->template_name,
+		       hdr_v1->template_name_len);
+		template_name[hdr_v1->template_name_len] = 0;
+
+		if (strcmp(template_name, "ima") == 0) {
+			pr_err("attempting to restore an unsupported \
+				template \"%s\" failed\n", template_name);
+			ret = -EINVAL;
+			break;
+		}
+
+		/* get template format */
+		template_desc = lookup_template_desc(template_name);
+		if (!template_desc) {
+			pr_err("template \"%s\" not found\n", template_name);
+			ret = -EINVAL;
+			break;
+		}
+
+		if (bufp > (bufendp - sizeof(data_v1->template_data_size))) {
+			pr_err("restoring the template data size failed\n");
+			ret = -EINVAL;
+			break;
+		}
+		bufp += (u_int8_t) sizeof(data_v1->template_data_size);
+
+		if (bufp > (bufendp - data_v1->template_data_size)) {
+			pr_err("restoring the template data failed\n");
+			ret = -EINVAL;
+			break;
+		}
+		bufp += data_v1->template_data_size;
+
+		ret = ima_restore_template_data(template_desc,
+						data_v1->template_data,
+						data_v1->template_data_size,
+						&entry);
+		if (ret < 0)
+			break;
+
+		memcpy(entry->digest, hdr_v1->digest, TPM_DIGEST_SIZE);
+		entry->pcr = hdr_v1->pcr;
+		ret = ima_restore_measurement_entry(entry);
+		if (ret < 0)
+			break;
+
+	}
+	return ret;
+}
-- 
2.1.0

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#1519041 — [PATCHC v7 01/10] powerpc: ima: Get the kexec buffer passed by the previous kernel

From: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>

The IMA kexec buffer allows the currently running kernel to pass
the measurement list via a kexec segment to the kernel that will be
kexec'd. The second kernel can check whether the previous kernel sent
the buffer and retrieve it.

This is the architecture-specific part which enables IMA to receive the
measurement list passed by the previous kernel. It will be used in the
next patch.

The change in machine_kexec_64.c is to factor out the logic of removing
an FDT memory reservation so that it can be used by remove_ima_buffer.

Changelog v6:
- The kexec_file_load patches v9 already define delete_fdt_mem_rsv,
  so now we just need to export it.

Changelog v5:
- New patch in this version. This code was previously in the kexec buffer
  handover patch series.

Changelog relative to kexec handover patches v5:
- Added CONFIG_HAVE_IMA_KEXEC.
- Added arch/powerpc/include/asm/ima.h.
- Moved code to arch/powerpc/kernel/ima_kexec.c.
- Renamed functions to variations of ima_kexec_buffer instead of
  variations of kexec_handover_buffer.
- Use a single property /chosen/linux,ima-kexec-buffer containing
  the buffer address and length, instead of
  /chosen/linux,kexec-handover-buffer-{start,end}.
- Use #address-cells and #size-cells to read the DT property.
- Use size_t instead of unsigned long for size arguments.
- Always remove linux,ima-kexec-buffer and its memory reservation
  when preparing a device tree for kexec_file_load.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 arch/Kconfig                                |   3 +
 arch/powerpc/Kconfig                        |   1 +
 arch/powerpc/include/asm/ima.h              |  13 +++
 arch/powerpc/include/asm/kexec.h            |   1 +
 arch/powerpc/kernel/Makefile                |   4 +
 arch/powerpc/kernel/ima_kexec.c             | 132 ++++++++++++++++++++++++++++
 arch/powerpc/kernel/machine_kexec_file_64.c |   5 +-
 7 files changed, 158 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/include/asm/ima.h
 create mode 100644 arch/powerpc/kernel/ima_kexec.c

diff --git a/arch/Kconfig b/arch/Kconfig
index 659bdd079277..e1605ff286a1 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -5,6 +5,9 @@
 config KEXEC_CORE
 	bool
 
+config HAVE_IMA_KEXEC
+	bool
+
 config OPROFILE
 	tristate "OProfile system profiling"
 	depends on PROFILING
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 897d0f14447d..40ee044f1915 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -458,6 +458,7 @@ config KEXEC
 config KEXEC_FILE
 	bool "kexec file based system call"
 	select KEXEC_CORE
+	select HAVE_IMA_KEXEC
 	select BUILD_BIN2C
 	depends on PPC64
 	depends on CRYPTO=y
diff --git a/arch/powerpc/include/asm/ima.h b/arch/powerpc/include/asm/ima.h
new file mode 100644
index 000000000000..d5a72dd9b499
--- /dev/null
+++ b/arch/powerpc/include/asm/ima.h
@@ -0,0 +1,13 @@
+#ifndef _ASM_POWERPC_IMA_H
+#define _ASM_POWERPC_IMA_H
+
+int ima_get_kexec_buffer(void **addr, size_t *size);
+int ima_free_kexec_buffer(void);
+
+#ifdef CONFIG_IMA
+void remove_ima_buffer(void *fdt, int chosen_node);
+#else
+static inline void remove_ima_buffer(void *fdt, int chosen_node) {}
+#endif
+
+#endif /* _ASM_POWERPC_IMA_H */
diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 4497db7555b0..23056d2dc330 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -101,6 +101,7 @@ int setup_purgatory(struct kimage *image, const void *slave_code,
 int setup_new_fdt(void *fdt, unsigned long initrd_load_addr,
 		  unsigned long initrd_len, const char *cmdline);
 bool find_debug_console(const void *fdt);
+int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size);
 #endif /* CONFIG_KEXEC_FILE */
 
 #else /* !CONFIG_KEXEC_CORE */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 424b13b1b2b0..c3b37171168c 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -111,6 +111,10 @@ obj-$(CONFIG_KEXEC_CORE)	+= machine_kexec.o crash.o \
 				   machine_kexec_$(BITS).o
 obj-$(CONFIG_KEXEC_FILE)	+= machine_kexec_file_$(BITS).o elf_util.o \
 				   kexec_elf_$(BITS).o
+ifeq ($(CONFIG_HAVE_IMA_KEXEC)$(CONFIG_IMA),yy)
+obj-y				+= ima_kexec.o
+endif
+
 obj-$(CONFIG_AUDIT)		+= audit.o
 obj64-$(CONFIG_AUDIT)		+= compat_audit.o
 
diff --git a/arch/powerpc/kernel/ima_kexec.c b/arch/powerpc/kernel/ima_kexec.c
new file mode 100644
index 000000000000..36e5a5df3804
--- /dev/null
+++ b/arch/powerpc/kernel/ima_kexec.c
@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2016 IBM Corporation
+ *
+ * Authors:
+ * Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/slab.h>
+#include <linux/kexec.h>
+#include <linux/of.h>
+#include <linux/memblock.h>
+#include <linux/libfdt.h>
+
+static int get_addr_size_cells(int *addr_cells, int *size_cells)
+{
+	struct device_node *root;
+
+	root = of_find_node_by_path("/");
+	if (!root)
+		return -EINVAL;
+
+	*addr_cells = of_n_addr_cells(root);
+	*size_cells = of_n_size_cells(root);
+
+	of_node_put(root);
+
+	return 0;
+}
+
+static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
+			       size_t *size)
+{
+	int ret, addr_cells, size_cells;
+
+	ret = get_addr_size_cells(&addr_cells, &size_cells);
+	if (ret)
+		return ret;
+
+	if (len < 4 * (addr_cells + size_cells))
+		return -ENOENT;
+
+	*addr = of_read_number(prop, addr_cells);
+	*size = of_read_number(prop + 4 * addr_cells, size_cells);
+
+	return 0;
+}
+
+/**
+ * ima_get_kexec_buffer - get IMA buffer from the previous kernel
+ * @addr:	On successful return, set to point to the buffer contents.
+ * @size:	On successful return, set to the buffer size.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int ima_get_kexec_buffer(void **addr, size_t *size)
+{
+	int ret, len;
+	unsigned long tmp_addr;
+	size_t tmp_size;
+	const void *prop;
+
+	prop = of_get_property(of_chosen, "linux,ima-kexec-buffer", &len);
+	if (!prop)
+		return -ENOENT;
+
+	ret = do_get_kexec_buffer(prop, len, &tmp_addr, &tmp_size);
+	if (ret)
+		return ret;
+
+	*addr = __va(tmp_addr);
+	*size = tmp_size;
+
+	return 0;
+}
+
+/**
+ * ima_free_kexec_buffer - free memory used by the IMA buffer
+ */
+int ima_free_kexec_buffer(void)
+{
+	int ret;
+	unsigned long addr;
+	size_t size;
+	struct property *prop;
+
+	prop = of_find_property(of_chosen, "linux,ima-kexec-buffer", NULL);
+	if (!prop)
+		return -ENOENT;
+
+	ret = do_get_kexec_buffer(prop->value, prop->length, &addr, &size);
+	if (ret)
+		return ret;
+
+	ret = of_remove_property(of_chosen, prop);
+	if (ret)
+		return ret;
+
+	return memblock_free(addr, size);
+
+}
+
+/**
+ * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt
+ *
+ * The IMA measurement buffer is of no use to a subsequent kernel, so we always
+ * remove it from the device tree.
+ */
+void remove_ima_buffer(void *fdt, int chosen_node)
+{
+	int ret, len;
+	unsigned long addr;
+	size_t size;
+	const void *prop;
+
+	prop = fdt_getprop(fdt, chosen_node, "linux,ima-kexec-buffer", &len);
+	if (!prop)
+		return;
+
+	ret = do_get_kexec_buffer(prop, len, &addr, &size);
+	fdt_delprop(fdt, chosen_node, "linux,ima-kexec-buffer");
+	if (ret)
+		return;
+
+	ret = delete_fdt_mem_rsv(fdt, addr, size);
+	if (!ret)
+		pr_debug("Removed old IMA buffer reservation.\n");
+}
diff --git a/arch/powerpc/kernel/machine_kexec_file_64.c b/arch/powerpc/kernel/machine_kexec_file_64.c
index 9acc56d199f0..7b13634f71bf 100644
--- a/arch/powerpc/kernel/machine_kexec_file_64.c
+++ b/arch/powerpc/kernel/machine_kexec_file_64.c
@@ -28,6 +28,7 @@
 #include <linux/of_fdt.h>
 #include <linux/libfdt.h>
 #include <asm/elf_util.h>
+#include <asm/ima.h>
 
 #define SLAVE_CODE_SIZE		256
 
@@ -363,7 +364,7 @@ int setup_purgatory(struct kimage *image, const void *slave_code,
  *
  * Return: 0 on success, or negative errno on error.
  */
-static int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)
+int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)
 {
 	int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
 
@@ -511,6 +512,8 @@ int setup_new_fdt(void *fdt, unsigned long initrd_load_addr,
 		}
 	}
 
+	remove_ima_buffer(fdt, chosen_node);
+
 	ret = fdt_setprop(fdt, chosen_node, "linux,booted-from-kexec", NULL, 0);
 	if (ret) {
 		pr_err("Error setting up the new device tree.\n");
-- 
2.1.0

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