diff mbox series

[v6,1/3] powerpc: Refactor kexec functions to move arch independent code to IMA

Message ID 20200908230856.9799-2-nramas@linux.microsoft.com (mailing list archive)
State New, archived
Headers show
Series Carry forward IMA measurement log on kexec on ARM64 | expand

Commit Message

Lakshmi Ramasubramanian Sept. 8, 2020, 11:08 p.m. UTC 
The functions ima_get_kexec_buffer(), ima_free_kexec_buffer(),
remove_ima_buffer(), and delete_fdt_mem_rsv() that handle carrying
forward the IMA measurement logs on kexec for powerpc do not have
architecture specific code, but they are currently defined for
powerpc only.

Move these functions to IMA subsystem so that it can be used for other
architectures as well. A later patch in this series will use these
functions for carrying forward the IMA measurement log for ARM64.
Rename remove_ima_buffer() to ima_remove_kexec_buffer().

Define FDT_PROP_IMA_KEXEC_BUFFER for the chosen node, namely
"linux,ima-kexec-buffer", that is added to the DTB to hold
the address and the size of the memory reserved to carry
the IMA measurement log.

Co-developed-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
 arch/powerpc/include/asm/ima.h          |  11 +--
 arch/powerpc/include/asm/kexec.h        |   1 -
 arch/powerpc/kexec/file_load.c          |  33 +-------
 arch/powerpc/kexec/ima.c                | 104 +-----------------------
 include/linux/ima.h                     |   2 +
 include/linux/kexec.h                   |  11 +++
 include/linux/libfdt.h                  |   3 +
 security/integrity/ima/Makefile         |   3 +-
 security/integrity/ima/ima.h            |   2 +
 security/integrity/ima/ima_fdt.c        |  80 ++++++++++++++++++
 security/integrity/ima/ima_kexec.c      |  58 +++++++++++++
 security/integrity/ima/ima_kexec_file.c |  51 ++++++++++++
 12 files changed, 214 insertions(+), 145 deletions(-)
 create mode 100644 security/integrity/ima/ima_fdt.c
 create mode 100644 security/integrity/ima/ima_kexec_file.c

Comments

Thiago Jung Bauermann Sept. 12, 2020, 3:18 a.m. UTC | #1 
Hello Lakshmi,

The code itself is good, I have just some minor comments about it.

But movement of powerpc code is unfortunately creating some issues. More
details below.

Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:

> diff --git a/arch/powerpc/kexec/ima.c b/arch/powerpc/kexec/ima.c
> index 720e50e490b6..467647886064 100644
> --- a/arch/powerpc/kexec/ima.c
> +++ b/arch/powerpc/kexec/ima.c
> @@ -9,6 +9,7 @@
>  #include <linux/slab.h>
>  #include <linux/kexec.h>
>  #include <linux/of.h>
> +#include <linux/ima.h>
>  #include <linux/memblock.h>
>  #include <linux/libfdt.h>
>  
> @@ -28,105 +29,6 @@ static int get_addr_size_cells(int *addr_cells, int *size_cells)
>  	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");
> -}
> -

With this change if CONFIG_IMA=y but CONFIG_IMA_KEXEC=n, this file will
only have static int get_addr_size_cells() as its contents, which isn't
useful (and will print a warning about the function not being used). You
should change the Makefile to only build this file if CONFIG_IMA_KEXEC=y.
Then you can also remove the #ifdef CONFIG_IMA_KEXEC/#endif within it as
well.

>  #ifdef CONFIG_IMA_KEXEC
>  /**
>   * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
> @@ -179,7 +81,7 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
>  	int ret, addr_cells, size_cells, entry_size;
>  	u8 value[16];
>  
> -	remove_ima_buffer(fdt, chosen_node);
> +	ima_remove_kexec_buffer(fdt, chosen_node);
>  	if (!image->arch.ima_buffer_size)
>  		return 0;
>  
> @@ -201,7 +103,7 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
>  	if (ret)
>  		return ret;
>  
> -	ret = fdt_setprop(fdt, chosen_node, "linux,ima-kexec-buffer", value,
> +	ret = fdt_setprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER, value,
>  			  entry_size);
>  	if (ret < 0)
>  		return -EINVAL;

<snip>

> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 9e93bef52968..00a60dcc7075 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -223,8 +223,19 @@ extern int crash_exclude_mem_range(struct crash_mem *mem,
>  				   unsigned long long mend);
>  extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
>  				       void **addr, unsigned long *sz);
> +
> +extern int delete_fdt_mem_rsv(void *fdt, unsigned long start,
> +			      unsigned long size);
>  #endif /* CONFIG_KEXEC_FILE */
>  
> +#ifndef CONFIG_KEXEC_FILE

I would use an `#else /* CONFIG_KEXEC_FILE */` here instead of #endif / #ifndef

> +static inline int delete_fdt_mem_rsv(void *fdt, unsigned long start,
> +				     unsigned long size)
> +{
> +	return 0;
> +}
> +#endif /* ifndef CONFIG_KEXEC_FILE */
> +
>  #ifdef CONFIG_KEXEC_ELF
>  struct kexec_elf_info {
>  	/*
> diff --git a/include/linux/libfdt.h b/include/linux/libfdt.h
> index 90ed4ebfa692..75fb40aa013b 100644
> --- a/include/linux/libfdt.h
> +++ b/include/linux/libfdt.h
> @@ -5,4 +5,7 @@
>  #include <linux/libfdt_env.h>
>  #include "../../scripts/dtc/libfdt/libfdt.h"
>  
> +/* Common device tree properties */
> +#define FDT_PROP_IMA_KEXEC_BUFFER	"linux,ima-kexec-buffer"
> +
>  #endif /* _INCLUDE_LIBFDT_H_ */
> diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
> index 67dabca670e2..05719fd28aec 100644
> --- a/security/integrity/ima/Makefile
> +++ b/security/integrity/ima/Makefile
> @@ -7,10 +7,11 @@
>  obj-$(CONFIG_IMA) += ima.o
>  
>  ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
> -	 ima_policy.o ima_template.o ima_template_lib.o
> +	 ima_policy.o ima_template.o ima_template_lib.o ima_fdt.o
>  ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
>  ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
>  ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
>  ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
>  ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
>  ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
> +ima-$(CONFIG_KEXEC_FILE) += ima_kexec_file.o

Even though you are using CONFIG_KEXEC_FILE here, AFAIK this will break
the powerpc build in the case of CONFIG_IMA=n and CONFIG_KEXEC_FILE=y
because the build system won't visit security/integrity/ima in that
case.

<snip>

> +/**
> + * ima_remove_kexec_buffer - remove the IMA buffer property and
> + *			     reservation from @fdt
> + *
> + * @fdt: Flattened Device Tree to update
> + * @chosen_node: Offset to the chosen node in the device tree
> + *
> + * The IMA measurement buffer is of no use to a subsequent kernel,
> + * so we always remove it from the device tree.
> + */
> +void ima_remove_kexec_buffer(void *fdt, int chosen_node)
> +{
> +	int ret, len;
> +	unsigned long addr;
> +	size_t size;
> +	const void *prop;
> +
> +	prop = fdt_getprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER, &len);
> +	if (!prop) {
> +		pr_err("Unable to find the ima kexec buffer node\n");

It's not an error if there's no IMA kexec buffer node. In case the
previous kernel didn't pass a buffer to this kernel there won't be one,
and it's fine. You should remove this pr_err().

> +		return;
> +	}
> +
> +	ret = do_get_kexec_buffer(prop, len, &addr, &size);
> +	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
> +	if (ret) {
> +		pr_err("Unable to delete the ima kexec buffer node\n");
> +		return;
> +	}
> +
> +	ret = delete_fdt_mem_rsv(fdt, addr, size);
> +	if (!ret)
> +		pr_err("Removed old IMA buffer reservation.\n");

Here you're printing an error when the function actually succeeded. You
should either change this back to a pr_debug(), or remove it.

> +}
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 121de3e04af2..ed70f99aeedc 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -10,8 +10,66 @@
>  #include <linux/seq_file.h>
>  #include <linux/vmalloc.h>
>  #include <linux/kexec.h>
> +#include <linux/of.h>
> +#include <linux/memblock.h>
> +#include <linux/libfdt.h>
> +#include <linux/ima.h>
>  #include "ima.h"
>  
> +/**
> + * 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.
> + */
> +static 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, FDT_PROP_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
> + */
> +static int ima_free_kexec_buffer(void)
> +{
> +	int ret;
> +	unsigned long addr;
> +	size_t size;
> +	struct property *prop;
> +
> +	prop = of_find_property(of_chosen, FDT_PROP_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);
> +
> +}
> +

Since you created ima_fdt.c, shouldn't the two functions above go in
that file instead of here, since they work with the device tree?

>  #ifdef CONFIG_IMA_KEXEC
>  static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
>  				     unsigned long segment_size)
> diff --git a/security/integrity/ima/ima_kexec_file.c b/security/integrity/ima/ima_kexec_file.c
> new file mode 100644
> index 000000000000..225e913e6ef2
> --- /dev/null
> +++ b/security/integrity/ima/ima_kexec_file.c
> @@ -0,0 +1,51 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (C) 2020 Microsoft Corporation
> + *
> + * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
> + *
> + * ima_kexec_file.c
> + *	Implements functions to handle device tree operations
> + */
> +
> +#include <linux/libfdt.h>
> +#include <linux/kexec.h>
> +#include <linux/types.h>
> +
> +/**
> + * delete_fdt_mem_rsv - delete memory reservation with given address and size
> + *
> + * @fdt: Flattened Device Tree to update
> + * @start: Starting address of the property to update

s/property to update/reservation to delete/

> + * @size: Size of the buffer corresponding to the given property

s/buffer corresponding to the given property/reservation to delete/

> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)

This function can't go in an IMA-specific directory, because it's used
in arch/powerpc/kexec/file_load.c even if IMA isn't enabled.

I'm not sure where would be a good place for it. Perhaps a new file
called kernel/kexec_file_fdt.c?

> +{
> +	int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
> +
> +	for (i = 0; i < num_rsvs; i++) {
> +		uint64_t rsv_start, rsv_size;
> +
> +		ret = fdt_get_mem_rsv(fdt, i, &rsv_start, &rsv_size);
> +		if (ret) {
> +			pr_err("Malformed device tree.\n");
> +			return -EINVAL;
> +		}
> +
> +		if (rsv_start == start && rsv_size == size) {
> +			ret = fdt_del_mem_rsv(fdt, i);
> +			if (ret) {
> +				pr_err("Error deleting device tree reservation.\n");
> +				return -EINVAL;
> +			}
> +
> +			pr_err("Freed the reserved memory at %lu of size %lu\n",
> +				start, size);

This isn't an error. You should change it to a pr_debug() or remove it.

> +			return 0;
> +		}
> +	}
> +
> +	return -ENOENT;
> +}
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/ima.h b/arch/powerpc/include/asm/ima.h
index ead488cf3981..188146ecbfaf 100644
--- a/arch/powerpc/include/asm/ima.h
+++ b/arch/powerpc/include/asm/ima.h
@@ -4,15 +4,6 @@ 
 
 struct kimage;
 
-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
-
 #ifdef CONFIG_IMA_KEXEC
 int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
 			      size_t size);
@@ -22,7 +13,7 @@  int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node);
 static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
 				   int chosen_node)
 {
-	remove_ima_buffer(fdt, chosen_node);
+	ima_remove_kexec_buffer(fdt, chosen_node);
 	return 0;
 }
 #endif /* CONFIG_IMA_KEXEC */
diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 55d6ede30c19..7c223031ecdd 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -126,7 +126,6 @@  int setup_purgatory(struct kimage *image, const void *slave_code,
 int setup_new_fdt(const struct kimage *image, void *fdt,
 		  unsigned long initrd_load_addr, unsigned long initrd_len,
 		  const char *cmdline);
-int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size);
 
 #ifdef CONFIG_PPC64
 struct kexec_buf;
diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
index 9a232bc36c8f..7a17655c530e 100644
--- a/arch/powerpc/kexec/file_load.c
+++ b/arch/powerpc/kexec/file_load.c
@@ -18,6 +18,7 @@ 
 #include <linux/kexec.h>
 #include <linux/of_fdt.h>
 #include <linux/libfdt.h>
+#include <linux/kexec.h>
 #include <asm/setup.h>
 #include <asm/ima.h>
 
@@ -109,38 +110,6 @@  int setup_purgatory(struct kimage *image, const void *slave_code,
 	return 0;
 }
 
-/**
- * delete_fdt_mem_rsv - delete memory reservation with given address and size
- *
- * Return: 0 on success, or negative errno on error.
- */
-int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)
-{
-	int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
-
-	for (i = 0; i < num_rsvs; i++) {
-		uint64_t rsv_start, rsv_size;
-
-		ret = fdt_get_mem_rsv(fdt, i, &rsv_start, &rsv_size);
-		if (ret) {
-			pr_err("Malformed device tree.\n");
-			return -EINVAL;
-		}
-
-		if (rsv_start == start && rsv_size == size) {
-			ret = fdt_del_mem_rsv(fdt, i);
-			if (ret) {
-				pr_err("Error deleting device tree reservation.\n");
-				return -EINVAL;
-			}
-
-			return 0;
-		}
-	}
-
-	return -ENOENT;
-}
-
 /*
  * setup_new_fdt - modify /chosen and memory reservation for the next kernel
  * @image:		kexec image being loaded.
diff --git a/arch/powerpc/kexec/ima.c b/arch/powerpc/kexec/ima.c
index 720e50e490b6..467647886064 100644
--- a/arch/powerpc/kexec/ima.c
+++ b/arch/powerpc/kexec/ima.c
@@ -9,6 +9,7 @@ 
 #include <linux/slab.h>
 #include <linux/kexec.h>
 #include <linux/of.h>
+#include <linux/ima.h>
 #include <linux/memblock.h>
 #include <linux/libfdt.h>
 
@@ -28,105 +29,6 @@  static int get_addr_size_cells(int *addr_cells, int *size_cells)
 	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");
-}
-
 #ifdef CONFIG_IMA_KEXEC
 /**
  * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
@@ -179,7 +81,7 @@  int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
 	int ret, addr_cells, size_cells, entry_size;
 	u8 value[16];
 
-	remove_ima_buffer(fdt, chosen_node);
+	ima_remove_kexec_buffer(fdt, chosen_node);
 	if (!image->arch.ima_buffer_size)
 		return 0;
 
@@ -201,7 +103,7 @@  int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
 	if (ret)
 		return ret;
 
-	ret = fdt_setprop(fdt, chosen_node, "linux,ima-kexec-buffer", value,
+	ret = fdt_setprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER, value,
 			  entry_size);
 	if (ret < 0)
 		return -EINVAL;
diff --git a/include/linux/ima.h b/include/linux/ima.h
index d15100de6cdd..e8e0afdfe783 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -26,6 +26,7 @@  extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
 extern void ima_post_path_mknod(struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
 extern void ima_kexec_cmdline(int kernel_fd, const void *buf, int size);
+extern void ima_remove_kexec_buffer(void *fdt, int chosen_node);
 
 #ifdef CONFIG_IMA_KEXEC
 extern void ima_add_kexec_buffer(struct kimage *image);
@@ -104,6 +105,7 @@  static inline int ima_file_hash(struct file *file, char *buf, size_t buf_size)
 }
 
 static inline void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) {}
+static inline void ima_remove_kexec_buffer(void *fdt, int chosen_node) {}
 #endif /* CONFIG_IMA */
 
 #ifndef CONFIG_IMA_KEXEC
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 9e93bef52968..00a60dcc7075 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -223,8 +223,19 @@  extern int crash_exclude_mem_range(struct crash_mem *mem,
 				   unsigned long long mend);
 extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
 				       void **addr, unsigned long *sz);
+
+extern int delete_fdt_mem_rsv(void *fdt, unsigned long start,
+			      unsigned long size);
 #endif /* CONFIG_KEXEC_FILE */
 
+#ifndef CONFIG_KEXEC_FILE
+static inline int delete_fdt_mem_rsv(void *fdt, unsigned long start,
+				     unsigned long size)
+{
+	return 0;
+}
+#endif /* ifndef CONFIG_KEXEC_FILE */
+
 #ifdef CONFIG_KEXEC_ELF
 struct kexec_elf_info {
 	/*
diff --git a/include/linux/libfdt.h b/include/linux/libfdt.h
index 90ed4ebfa692..75fb40aa013b 100644
--- a/include/linux/libfdt.h
+++ b/include/linux/libfdt.h
@@ -5,4 +5,7 @@ 
 #include <linux/libfdt_env.h>
 #include "../../scripts/dtc/libfdt/libfdt.h"
 
+/* Common device tree properties */
+#define FDT_PROP_IMA_KEXEC_BUFFER	"linux,ima-kexec-buffer"
+
 #endif /* _INCLUDE_LIBFDT_H_ */
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 67dabca670e2..05719fd28aec 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -7,10 +7,11 @@ 
 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_policy.o ima_template.o ima_template_lib.o ima_fdt.o
 ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
 ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
 ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 ima-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
 ima-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
 ima-$(CONFIG_IMA_QUEUE_EARLY_BOOT_KEYS) += ima_queue_keys.o
+ima-$(CONFIG_KEXEC_FILE) += ima_kexec_file.o
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 38043074ce5e..0d2bfe53be69 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -167,6 +167,8 @@  void ima_init_template_list(void);
 int __init ima_init_digests(void);
 int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
 			  void *lsm_data);
+int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
+			size_t *size);
 
 /*
  * used to protect h_table and sha_table
diff --git a/security/integrity/ima/ima_fdt.c b/security/integrity/ima/ima_fdt.c
new file mode 100644
index 000000000000..8c4cb580b772
--- /dev/null
+++ b/security/integrity/ima/ima_fdt.c
@@ -0,0 +1,80 @@ 
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 Microsoft Corporation
+ *
+ * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
+ *
+ * ima_fdt.c
+ *	Implements functions to handle IMA buffer in device tree
+ */
+
+#include <linux/libfdt.h>
+#include <linux/kexec.h>
+#include <linux/ima.h>
+#include "ima.h"
+
+/**
+ * do_get_kexec_buffer - Get address and size of IMA kexec buffer
+ *
+ * @prop: IMA kexec buffer node in the device tree
+ * @addr: Return address of the node
+ * @size: Return size of the node
+ */
+int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
+			size_t *size)
+{
+	int addr_cells, 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);
+
+	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_remove_kexec_buffer - remove the IMA buffer property and
+ *			     reservation from @fdt
+ *
+ * @fdt: Flattened Device Tree to update
+ * @chosen_node: Offset to the chosen node in the device tree
+ *
+ * The IMA measurement buffer is of no use to a subsequent kernel,
+ * so we always remove it from the device tree.
+ */
+void ima_remove_kexec_buffer(void *fdt, int chosen_node)
+{
+	int ret, len;
+	unsigned long addr;
+	size_t size;
+	const void *prop;
+
+	prop = fdt_getprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER, &len);
+	if (!prop) {
+		pr_err("Unable to find the ima kexec buffer node\n");
+		return;
+	}
+
+	ret = do_get_kexec_buffer(prop, len, &addr, &size);
+	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
+	if (ret) {
+		pr_err("Unable to delete the ima kexec buffer node\n");
+		return;
+	}
+
+	ret = delete_fdt_mem_rsv(fdt, addr, size);
+	if (!ret)
+		pr_err("Removed old IMA buffer reservation.\n");
+}
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 121de3e04af2..ed70f99aeedc 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -10,8 +10,66 @@ 
 #include <linux/seq_file.h>
 #include <linux/vmalloc.h>
 #include <linux/kexec.h>
+#include <linux/of.h>
+#include <linux/memblock.h>
+#include <linux/libfdt.h>
+#include <linux/ima.h>
 #include "ima.h"
 
+/**
+ * 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.
+ */
+static 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, FDT_PROP_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
+ */
+static int ima_free_kexec_buffer(void)
+{
+	int ret;
+	unsigned long addr;
+	size_t size;
+	struct property *prop;
+
+	prop = of_find_property(of_chosen, FDT_PROP_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);
+
+}
+
 #ifdef CONFIG_IMA_KEXEC
 static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
 				     unsigned long segment_size)
diff --git a/security/integrity/ima/ima_kexec_file.c b/security/integrity/ima/ima_kexec_file.c
new file mode 100644
index 000000000000..225e913e6ef2
--- /dev/null
+++ b/security/integrity/ima/ima_kexec_file.c
@@ -0,0 +1,51 @@ 
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 Microsoft Corporation
+ *
+ * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
+ *
+ * ima_kexec_file.c
+ *	Implements functions to handle device tree operations
+ */
+
+#include <linux/libfdt.h>
+#include <linux/kexec.h>
+#include <linux/types.h>
+
+/**
+ * delete_fdt_mem_rsv - delete memory reservation with given address and size
+ *
+ * @fdt: Flattened Device Tree to update
+ * @start: Starting address of the property to update
+ * @size: Size of the buffer corresponding to the given property
+ *
+ * Return: 0 on success, or negative errno on error.
+ */
+int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)
+{
+	int i, ret, num_rsvs = fdt_num_mem_rsv(fdt);
+
+	for (i = 0; i < num_rsvs; i++) {
+		uint64_t rsv_start, rsv_size;
+
+		ret = fdt_get_mem_rsv(fdt, i, &rsv_start, &rsv_size);
+		if (ret) {
+			pr_err("Malformed device tree.\n");
+			return -EINVAL;
+		}
+
+		if (rsv_start == start && rsv_size == size) {
+			ret = fdt_del_mem_rsv(fdt, i);
+			if (ret) {
+				pr_err("Error deleting device tree reservation.\n");
+				return -EINVAL;
+			}
+
+			pr_err("Freed the reserved memory at %lu of size %lu\n",
+				start, size);
+			return 0;
+		}
+	}
+
+	return -ENOENT;
+}