[PATCH v4 0/5] Carry forward IMA measurement log on kexec on ARM64

[PATCH v4 0/5] Carry forward IMA measurement log on kexec on ARM64

[Lakshmi Ramasubramanian]

On kexec file load Integrgity 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
the measurement through the IMA log 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.
However in the current implementation the IMA measurement logs are not
carried over on ARM64 platforms. Therefore a remote attestation service
cannot verify the authenticity of the running kernel on ARM64 platforms
when the kernel is updated through the kexec system call.

This patch series adds support for carrying forward the IMA measurement
log on kexec on ARM64. powerpc already supports carrying forward
the IMA measurement log on kexec.

This series refactors the platform independent code such that it can be
reused for ARM64 as well. A chosen node namely
"linux,ima-kexec-buffer" is added to the DTB for ARM64 to hold
the address and the size of the memory reserved to carry
the IMA measurement log.

This patch series has been tested for ARM64 platform using QEMU.
I would like help from the community for testing this change on powerpc.
Thanks.

This series is based on commit 18445bf405cb ("Merge tag 'spi-fix-v5.9-rc1'
of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi") in
https://github.com/torvalds/linux "master" branch.

Changelog:

v4:
  - Submitting the patch series on behalf of the original author
    Prakhar Srivastava <prsriva@linux.microsoft.com>
  - Moved FDT_PROP_IMA_KEXEC_BUFFER ("linux,ima-kexec-buffer") to
    libfdt.h so that it can be shared by multiple platforms.

v3:
Breakup patches further into separate patches.
  - Refactoring non architecture specific code out of powerpc
  - Update powerpc related code to use fdt functions
  - Update IMA buffer read related code to use of functions
  - Add support to store the memory information of the IMA
    measurement logs to be carried forward.
  - Update the property strings to align with documented nodes
    https://github.com/devicetree-org/dt-schema/pull/46

v2:
  Break patches into separate patches.
  - Powerpc related Refactoring
  - Updating the docuemntation for chosen node
  - Updating arm64 to support IMA buffer pass

v1:
  Refactoring carrying over IMA measuremnet logs over Kexec. This patch
    moves the non-architecture specific code out of powerpc and adds to
    security/ima.(Suggested by Thiago)
  Add Documentation regarding the ima-kexec-buffer node in the chosen
    node documentation

v0:
  Add a layer of abstraction to use the memory reserved by device tree
    for ima buffer pass.
  Add support for ima buffer pass using reserved memory for arm64 kexec.
    Update the arch sepcific code path in kexec file load to store the
    ima buffer in the reserved memory. The same reserved memory is read
    on kexec or cold boot.

Lakshmi Ramasubramanian (5):
  powerpc: Refactor kexec functions to move arch independent code to IMA
  powerpc: Use libfdt functions to fetch IMA buffer properties
  IMA: Refactor do_get_kexec_buffer() to call of_ functions directly
  arm64: Store IMA log information in kimage used for kexec
  arm64: Add IMA kexec buffer to DTB

 arch/arm64/Kconfig                     |   1 +
 arch/arm64/include/asm/ima.h           |  17 ++++
 arch/arm64/include/asm/kexec.h         |   3 +
 arch/arm64/kernel/machine_kexec_file.c |  28 ++++++
 arch/powerpc/include/asm/ima.h         |   3 -
 arch/powerpc/kexec/ima.c               | 123 ++++++-------------------
 include/linux/libfdt.h                 |   3 +
 security/integrity/ima/ima_kexec.c     |  81 ++++++++++++++++
 8 files changed, 161 insertions(+), 98 deletions(-)
 create mode 100644 arch/arm64/include/asm/ima.h

-- 
2.28.0

[PATCH v4 1/5] powerpc: Refactor kexec functions to move arch independent code to IMA

[Lakshmi Ramasubramanian]

The functions ima_get_kexec_buffer() and ima_free_kexec_buffer() 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.

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     |  3 -
 arch/powerpc/kexec/ima.c           | 60 +-------------------
 include/linux/libfdt.h             |  3 +
 security/integrity/ima/ima_kexec.c | 91 ++++++++++++++++++++++++++++++
 4 files changed, 97 insertions(+), 60 deletions(-)

diff --git a/arch/powerpc/include/asm/ima.h b/arch/powerpc/include/asm/ima.h
index ead488cf3981..bc27fd94de52 100644
--- a/arch/powerpc/include/asm/ima.h
+++ b/arch/powerpc/include/asm/ima.h
@@ -4,9 +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
diff --git a/arch/powerpc/kexec/ima.c b/arch/powerpc/kexec/ima.c
index 720e50e490b6..f5112ee4bb0b 100644
--- a/arch/powerpc/kexec/ima.c
+++ b/arch/powerpc/kexec/ima.c
@@ -46,60 +46,6 @@ static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
 	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
  *
@@ -113,12 +59,12 @@ void remove_ima_buffer(void *fdt, int chosen_node)
 	size_t size;
 	const void *prop;
 
-	prop = fdt_getprop(fdt, chosen_node, "linux,ima-kexec-buffer", &len);
+	prop = fdt_getprop(fdt, chosen_node, FDT_PROP_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");
+	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
 	if (ret)
 		return;
 
@@ -201,7 +147,7 @@ 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/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/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 121de3e04af2..25d79d521597 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -10,8 +10,99 @@
 #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 "ima.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, 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
+ */
+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)
-- 
2.28.0

Re: [PATCH v4 1/5] powerpc: Refactor kexec functions to move arch independent code to IMA

[Thiago Jung Bauermann]

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

> The functions ima_get_kexec_buffer() and ima_free_kexec_buffer() 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.
>
> 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>

This patch removes two functions from arch/powerpc/kexec/ima.c, but adds
four to security/integrity/ima/ima_kexec.c. The extra ones are
get_addr_size_cells() and do_get_kexec_buffer(), which are being copied
from the powerpc code but can't be removed yet because they're still
used there by remove_ima_buffer() and setup_ima_buffer().

On the next patch you remove the need for these functions in powerpc
code and therefore delete them. This confused me at first, so I think it
would be cleared if you put patch 2 first in the series and then on this
patch you can simply move the four functions and delete them from
arch/powerpc/kexec/ima.c.

If you prefer to keep the current order, it's worth mentioning on the
commit log where get_addr_size_cells() and do_get_kexec_buffer() are
coming from.

Regardless:

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH v4 1/5] powerpc: Refactor kexec functions to move arch independent code to IMA

[Lakshmi Ramasubramanian]

On 8/27/20 4:35 PM, Thiago Jung Bauermann wrote:
> 
> Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:
> 
>> The functions ima_get_kexec_buffer() and ima_free_kexec_buffer() 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.
>>
>> 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>
> 
> This patch removes two functions from arch/powerpc/kexec/ima.c, but adds
> four to security/integrity/ima/ima_kexec.c. The extra ones are
> get_addr_size_cells() and do_get_kexec_buffer(), which are being copied
> from the powerpc code but can't be removed yet because they're still
> used there by remove_ima_buffer() and setup_ima_buffer().
> 
> On the next patch you remove the need for these functions in powerpc
> code and therefore delete them. This confused me at first, so I think it
> would be cleared if you put patch 2 first in the series and then on this
> patch you can simply move the four functions and delete them from
> arch/powerpc/kexec/ima.c.
> 
> If you prefer to keep the current order, it's worth mentioning on the
> commit log where get_addr_size_cells() and do_get_kexec_buffer() are
> coming from.
> 
> Regardless:
> 
> Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> 

Thanks for reviewing the changes Thiago.

I'll update the commit log to describe the changes related to 
get_addr_size_cells() and do_get_kexec_buffer().

  -lakshmi

Re: [PATCH v4 1/5] powerpc: Refactor kexec functions to move arch independent code to IMA

[Thiago Jung Bauermann]

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

> +/**
> + * 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)

I just noticed that this function is only called from within
ima_kexec.c, so it can be made static.

> +{
> +	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
> + */
> +int ima_free_kexec_buffer(void)

This one can be static as well.

> +{
> +	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)


-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH v4 1/5] powerpc: Refactor kexec functions to move arch independent code to IMA

[Lakshmi Ramasubramanian]

On 8/27/20 6:23 PM, Thiago Jung Bauermann wrote:
> 
> Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:
> 
>> +/**
>> + * 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)
> 
> I just noticed that this function is only called from within
> ima_kexec.c, so it can be made static.

Will do.

> 
>> +{
>> +	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
>> + */
>> +int ima_free_kexec_buffer(void)
> 
> This one can be static as well.

Will do.

  -lakshmi

> 
>> +{
>> +	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)
> 
> 

[PATCH v4 2/5] powerpc: Use libfdt functions to fetch IMA buffer properties

[Lakshmi Ramasubramanian]

remove_ima_buffer() uses custom code to handle properties of
the IMA buffer, such as the buffer's address, size, etc., in 
the device tree. Flat Device Tree (FDT) library (libfdt) provides
helper functions for handling device tree node properties and
they should be used instead.

Use libfdt functions for handling IMA buffer properties in
the device tree node for powerpc.

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/kexec/ima.c | 63 ++++++++++++++++------------------------
 1 file changed, 25 insertions(+), 38 deletions(-)

diff --git a/arch/powerpc/kexec/ima.c b/arch/powerpc/kexec/ima.c
index f5112ee4bb0b..573ff708d700 100644
--- a/arch/powerpc/kexec/ima.c
+++ b/arch/powerpc/kexec/ima.c
@@ -12,40 +12,6 @@
 #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;
-}
-
 /**
  * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt
  *
@@ -54,7 +20,7 @@ static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
  */
 void remove_ima_buffer(void *fdt, int chosen_node)
 {
-	int ret, len;
+	int ret, len, addr_cells, size_cells;
 	unsigned long addr;
 	size_t size;
 	const void *prop;
@@ -63,7 +29,22 @@ void remove_ima_buffer(void *fdt, int chosen_node)
 	if (!prop)
 		return;
 
-	ret = do_get_kexec_buffer(prop, len, &addr, &size);
+	ret = fdt_address_cells(fdt, chosen_node);
+	if (ret < 0)
+		return;
+	addr_cells = ret;
+
+	ret = fdt_size_cells(fdt, chosen_node);
+	if (ret < 0)
+		return;
+	size_cells = ret;
+
+	if (len < 4 * (addr_cells + size_cells))
+		return;
+
+	addr = of_read_number(prop, addr_cells);
+	size = of_read_number(prop + 4 * addr_cells, size_cells);
+
 	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
 	if (ret)
 		return;
@@ -129,9 +110,15 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
 	if (!image->arch.ima_buffer_size)
 		return 0;
 
-	ret = get_addr_size_cells(&addr_cells, &size_cells);
-	if (ret)
+	ret = fdt_address_cells(fdt, chosen_node);
+	if (ret < 0)
+		return ret;
+	addr_cells = ret;
+
+	ret = fdt_size_cells(fdt, chosen_node);
+	if (ret < 0)
 		return ret;
+	size_cells = ret;
 
 	entry_size = 4 * (addr_cells + size_cells);
 
-- 
2.28.0

Re: [PATCH v4 2/5] powerpc: Use libfdt functions to fetch IMA buffer properties

[Thiago Jung Bauermann]

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

> @@ -63,7 +29,22 @@ void remove_ima_buffer(void *fdt, int chosen_node)
>  	if (!prop)
>  		return;
>  
> -	ret = do_get_kexec_buffer(prop, len, &addr, &size);
> +	ret = fdt_address_cells(fdt, chosen_node);

This change was already present in the previous version of the patch but
it was just today that I noticed a problem: there's no #address-cells
property in /chosen. This code will still work though because if there's
no property this function returns 2 which is the correct value for
ppc64. But it's conceptually wrong. You need to pass the node offset for
/ so that it gets the #address-cells property from there.

> +	if (ret < 0)
> +		return;
> +	addr_cells = ret;
> +
> +	ret = fdt_size_cells(fdt, chosen_node);

Here we're not so lucky. The default value returned when no #size-cells
property is present is 1, which is wrong for ppc64 so this change
introduces a bug. You also need to pass the node offset for / here.

> +	if (ret < 0)
> +		return;
> +	size_cells = ret;
> +
> +	if (len < 4 * (addr_cells + size_cells))
> +		return;
> +
> +	addr = of_read_number(prop, addr_cells);
> +	size = of_read_number(prop + 4 * addr_cells, size_cells);
> +
>  	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
>  	if (ret)
>  		return;
> @@ -129,9 +110,15 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
>  	if (!image->arch.ima_buffer_size)
>  		return 0;
>  
> -	ret = get_addr_size_cells(&addr_cells, &size_cells);
> -	if (ret)
> +	ret = fdt_address_cells(fdt, chosen_node);
> +	if (ret < 0)
> +		return ret;
> +	addr_cells = ret;
> +
> +	ret = fdt_size_cells(fdt, chosen_node);
> +	if (ret < 0)
>  		return ret;
> +	size_cells = ret;
>  
>  	entry_size = 4 * (addr_cells + size_cells);

Ditto here.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

Re: [PATCH v4 2/5] powerpc: Use libfdt functions to fetch IMA buffer properties

[Lakshmi Ramasubramanian]

On 8/27/20 4:50 PM, Thiago Jung Bauermann wrote:
> 
> Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:
> 
>> @@ -63,7 +29,22 @@ void remove_ima_buffer(void *fdt, int chosen_node)
>>   	if (!prop)
>>   		return;
>>   
>> -	ret = do_get_kexec_buffer(prop, len, &addr, &size);
>> +	ret = fdt_address_cells(fdt, chosen_node);
> 
> This change was already present in the previous version of the patch but
> it was just today that I noticed a problem: there's no #address-cells
> property in /chosen. This code will still work though because if there's
> no property this function returns 2 which is the correct value for
> ppc64. But it's conceptually wrong. You need to pass the node offset for
> / so that it gets the #address-cells property from there.

Thanks for the info.
Will fix this.

> 
>> +	if (ret < 0)
>> +		return;
>> +	addr_cells = ret;
>> +
>> +	ret = fdt_size_cells(fdt, chosen_node);
> 
> Here we're not so lucky. The default value returned when no #size-cells
> property is present is 1, which is wrong for ppc64 so this change
> introduces a bug. You also need to pass the node offset for / here.

Will fix this.

> 
>> +	if (ret < 0)
>> +		return;
>> +	size_cells = ret;
>> +
>> +	if (len < 4 * (addr_cells + size_cells))
>> +		return;
>> +
>> +	addr = of_read_number(prop, addr_cells);
>> +	size = of_read_number(prop + 4 * addr_cells, size_cells);
>> +
>>   	fdt_delprop(fdt, chosen_node, FDT_PROP_IMA_KEXEC_BUFFER);
>>   	if (ret)
>>   		return;
>> @@ -129,9 +110,15 @@ int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node)
>>   	if (!image->arch.ima_buffer_size)
>>   		return 0;
>>   
>> -	ret = get_addr_size_cells(&addr_cells, &size_cells);
>> -	if (ret)
>> +	ret = fdt_address_cells(fdt, chosen_node);
>> +	if (ret < 0)
>> +		return ret;
>> +	addr_cells = ret;
>> +
>> +	ret = fdt_size_cells(fdt, chosen_node);
>> +	if (ret < 0)
>>   		return ret;
>> +	size_cells = ret;
>>   
>>   	entry_size = 4 * (addr_cells + size_cells);
> 
> Ditto here.
> 

Will fix this.

thanks,
  -lakshmi

[PATCH v4 3/5] IMA: Refactor do_get_kexec_buffer() to call of_ functions directly

[Lakshmi Ramasubramanian]

do_get_kexec_buffer() calls another local function get_addr_size_cells()
to get the address and size of the IMA measurement log buffer stored in
the device tree. get_addr_size_cells() is small enough that it can be
merged into do_get_kexec_buffer() and a function call can be avoided.

Refactor do_get_kexec_buffer() to call of_ functions directly instead
of calling get_addr_size_cells() and remove get_addr_size_cells().

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>
---
 security/integrity/ima/ima_kexec.c | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 25d79d521597..283631098b48 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -15,31 +15,21 @@
 #include <linux/libfdt.h>
 #include "ima.h"
 
-static int get_addr_size_cells(int *addr_cells, int *size_cells)
+static 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);
+	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;
 
-- 
2.28.0

Re: [PATCH v4 3/5] IMA: Refactor do_get_kexec_buffer() to call of_ functions directly

[Thiago Jung Bauermann]

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

> do_get_kexec_buffer() calls another local function get_addr_size_cells()
> to get the address and size of the IMA measurement log buffer stored in
> the device tree. get_addr_size_cells() is small enough that it can be
> merged into do_get_kexec_buffer() and a function call can be avoided.
>
> Refactor do_get_kexec_buffer() to call of_ functions directly instead
> of calling get_addr_size_cells() and remove get_addr_size_cells().
>
> 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>

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

[PATCH v4 4/5] arm64: Store IMA log information in kimage used for kexec

[Lakshmi Ramasubramanian]

Address and size of the buffer containing the IMA measurement log need
to be passed from the current kernel to the next kernel on kexec.

Add address and size fields to "struct kimage_arch" for ARM64 platform
to hold the address and size of the IMA measurement log buffer.
Define an architecture specific function for ARM64 namely
arch_ima_add_kexec_buffer() that will set the address and size of
the current kernel's IMA buffer to be passed to the next kernel on kexec.

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/arm64/include/asm/ima.h           | 17 +++++++++++++++++
 arch/arm64/include/asm/kexec.h         |  3 +++
 arch/arm64/kernel/machine_kexec_file.c | 17 +++++++++++++++++
 3 files changed, 37 insertions(+)
 create mode 100644 arch/arm64/include/asm/ima.h

diff --git a/arch/arm64/include/asm/ima.h b/arch/arm64/include/asm/ima.h
new file mode 100644
index 000000000000..70ac39b74607
--- /dev/null
+++ b/arch/arm64/include/asm/ima.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_ARCH_IMA_H
+#define _ASM_ARCH_IMA_H
+
+struct kimage;
+
+#ifdef CONFIG_IMA_KEXEC
+int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
+			      size_t size);
+#else
+static inline int arch_ima_add_kexec_buffer(struct kimage *image,
+			unsigned long load_addr, size_t size)
+{
+	return 0;
+}
+#endif /* CONFIG_IMA_KEXEC */
+#endif /* _ASM_ARCH_IMA_H */
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index d24b527e8c00..7bd60c185ad3 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -100,6 +100,9 @@ struct kimage_arch {
 	void *elf_headers;
 	unsigned long elf_headers_mem;
 	unsigned long elf_headers_sz;
+
+	phys_addr_t ima_buffer_addr;
+	size_t ima_buffer_size;
 };
 
 extern const struct kexec_file_ops kexec_image_ops;
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 361a1143e09e..4c54723e7a04 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -38,6 +38,23 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
 	NULL
 };
 
+/**
+ * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
+ *
+ * Architectures should use this function to pass on the IMA buffer
+ * information to the next kernel.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
+			      size_t size)
+{
+	image->arch.ima_buffer_addr = load_addr;
+	image->arch.ima_buffer_size = size;
+	return 0;
+}
+
+
 int arch_kimage_file_post_load_cleanup(struct kimage *image)
 {
 	vfree(image->arch.dtb);
-- 
2.28.0

Re: [PATCH v4 4/5] arm64: Store IMA log information in kimage used for kexec

[Thiago Jung Bauermann]

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

> Address and size of the buffer containing the IMA measurement log need
> to be passed from the current kernel to the next kernel on kexec.
>
> Add address and size fields to "struct kimage_arch" for ARM64 platform
> to hold the address and size of the IMA measurement log buffer.
> Define an architecture specific function for ARM64 namely
> arch_ima_add_kexec_buffer() that will set the address and size of
> the current kernel's IMA buffer to be passed to the next kernel on kexec.
>
> 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>

Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>

IMHO this patch and the next one can be squashed together. Also, a minor
comment below.

> ---
>  arch/arm64/include/asm/ima.h           | 17 +++++++++++++++++
>  arch/arm64/include/asm/kexec.h         |  3 +++
>  arch/arm64/kernel/machine_kexec_file.c | 17 +++++++++++++++++
>  3 files changed, 37 insertions(+)
>  create mode 100644 arch/arm64/include/asm/ima.h
>
> diff --git a/arch/arm64/include/asm/ima.h b/arch/arm64/include/asm/ima.h
> new file mode 100644
> index 000000000000..70ac39b74607
> --- /dev/null
> +++ b/arch/arm64/include/asm/ima.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_ARCH_IMA_H
> +#define _ASM_ARCH_IMA_H
> +
> +struct kimage;
> +
> +#ifdef CONFIG_IMA_KEXEC
> +int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
> +			      size_t size);
> +#else
> +static inline int arch_ima_add_kexec_buffer(struct kimage *image,
> +			unsigned long load_addr, size_t size)
> +{
> +	return 0;
> +}

There's no need to define arch_ima_add_kexec_buffer() if
CONFIG_IMA_KEXEC isn't set because in that case, the code which calls
this function in ima_add_kexec_buffer() won't be part of the build.

> +#endif /* CONFIG_IMA_KEXEC */
> +#endif /* _ASM_ARCH_IMA_H */

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

[PATCH v4 5/5] arm64: Add IMA kexec buffer to DTB

[Lakshmi Ramasubramanian]

The address and size of the current kernel's IMA measurement log
need to be added to the device tree's IMA kexec buffer node for
the log to be carried over to the next kernel on the kexec call.

Add the IMA measurement log buffer properties to the device tree for
ARM64. Update CONFIG_KEXEC_FILE to select CONFIG_HAVE_IMA_KEXEC to
indicate that the IMA measurement log information is present in
the device tree.

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/arm64/Kconfig                     |  1 +
 arch/arm64/kernel/machine_kexec_file.c | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6d232837cbee..9f03c8245e5b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1077,6 +1077,7 @@ config KEXEC
 config KEXEC_FILE
 	bool "kexec file based system call"
 	select KEXEC_CORE
+	select HAVE_IMA_KEXEC
 	help
 	  This is new version of kexec system call. This system call is
 	  file based and takes file descriptors as system call argument
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 4c54723e7a04..8488f8e87d1a 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -153,6 +153,17 @@ static int setup_dtb(struct kimage *image,
 				FDT_PROP_KASLR_SEED);
 	}
 
+	/* add ima-kexec-buffer */
+	if (image->arch.ima_buffer_size > 0) {
+
+		ret = fdt_appendprop_addrrange(dtb, 0, off,
+				FDT_PROP_IMA_KEXEC_BUFFER,
+				image->arch.ima_buffer_addr,
+				image->arch.ima_buffer_size);
+		if (ret)
+			return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
+	}
+
 	/* add rng-seed */
 	if (rng_is_initialized()) {
 		void *rng_seed;
-- 
2.28.0

Re: [PATCH v4 5/5] arm64: Add IMA kexec buffer to DTB

[Thiago Jung Bauermann]

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

> The address and size of the current kernel's IMA measurement log
> need to be added to the device tree's IMA kexec buffer node for
> the log to be carried over to the next kernel on the kexec call.
>
> Add the IMA measurement log buffer properties to the device tree for
> ARM64. Update CONFIG_KEXEC_FILE to select CONFIG_HAVE_IMA_KEXEC to
> indicate that the IMA measurement log information is present in
> the device tree.
>
> 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/arm64/Kconfig                     |  1 +
>  arch/arm64/kernel/machine_kexec_file.c | 11 +++++++++++
>  2 files changed, 12 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 6d232837cbee..9f03c8245e5b 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1077,6 +1077,7 @@ config KEXEC
>  config KEXEC_FILE
>  	bool "kexec file based system call"
>  	select KEXEC_CORE
> +	select HAVE_IMA_KEXEC
>  	help
>  	  This is new version of kexec system call. This system call is
>  	  file based and takes file descriptors as system call argument
> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> index 4c54723e7a04..8488f8e87d1a 100644
> --- a/arch/arm64/kernel/machine_kexec_file.c
> +++ b/arch/arm64/kernel/machine_kexec_file.c
> @@ -153,6 +153,17 @@ static int setup_dtb(struct kimage *image,
>  				FDT_PROP_KASLR_SEED);
>  	}
>  
> +	/* add ima-kexec-buffer */
> +	if (image->arch.ima_buffer_size > 0) {
> +
> +		ret = fdt_appendprop_addrrange(dtb, 0, off,
> +				FDT_PROP_IMA_KEXEC_BUFFER,
> +				image->arch.ima_buffer_addr,
> +				image->arch.ima_buffer_size);
> +		if (ret)
> +			return (ret == -FDT_ERR_NOSPACE ? -ENOMEM : -EINVAL);
> +	}
> +
>  	/* add rng-seed */
>  	if (rng_is_initialized()) {
>  		void *rng_seed;

I believe you need to add a memory reservation to the dtb covering the
IMA kexec buffer, otherwise nothing stops the new kernel from stomping
over it. E.g., powerpc does:

	ret = fdt_add_mem_rsv(fdt, image->arch.ima_buffer_addr,
			      image->arch.ima_buffer_size);

-- 
Thiago Jung Bauermann
IBM Linux Technology Center