diff mbox series

[v6,3/7] ima: kexec: skip IMA segment validation after kexec soft reboot

Message ID 20250124225547.22684-4-chenste@linux.microsoft.com (mailing list archive)
State New
Headers show
Series ima: kexec: measure events between kexec load and excute | expand

Commit Message

steven chen Jan. 24, 2025, 10:55 p.m. UTC 
kexec_calculate_store_digests() calculates and stores the digest of the
segment at kexec_file_load syscall where the IMA segment is also
allocated.  With this series, the IMA segment will be updated with the
measurement log at kexec soft reboot.  Therefore, it may fail digest
verification in verify_sha256_digest() after kexec soft reboot into the
new Kernel.  Therefore, the digest calculation/verification of the IMA
segment needs to be skipped.

Skip IMA segment from calculating and storing digest in function
kexec_calculate_store_digests() so that it is not added to the
'purgatory_sha_regions'.

Since verify_sha256_digest() only verifies 'purgatory_sha_regions',
no change is needed in verify_sha256_digest() in this context.

With this change, the IMA segment is not included in the digest
calculation, storage, and verification.

Author: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: steven chen <chenste@linux.microsoft.com>
---
 include/linux/kexec.h              |  3 +++
 kernel/kexec_file.c                | 10 ++++++++++
 security/integrity/ima/ima_kexec.c |  3 +++
 3 files changed, 16 insertions(+)

Comments

Stefan Berger Jan. 28, 2025, 3:23 p.m. UTC | #1 
On 1/24/25 5:55 PM, steven chen wrote:
> kexec_calculate_store_digests() calculates and stores the digest of the
> segment at kexec_file_load syscall where the IMA segment is also
> allocated.  With this series, the IMA segment will be updated with the
> measurement log at kexec soft reboot.  Therefore, it may fail digest

... log at kexec execute stage when the soft reboot is initiated.

> verification in verify_sha256_digest() after kexec soft reboot into the
 > new Kernel.  Therefore, the digest calculation/verification of the IMA

kernel

> segment needs to be skipped.
> 
> Skip IMA segment from calculating and storing digest in function
> kexec_calculate_store_digests() so that it is not added to the
> 'purgatory_sha_regions'.
> 
> Since verify_sha256_digest() only verifies 'purgatory_sha_regions',
> no change is needed in verify_sha256_digest() in this context.
> 
> With this change, the IMA segment is not included in the digest
> calculation, storage, and verification.
> 
> Author: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
> Signed-off-by: steven chen <chenste@linux.microsoft.com>
> ---
>   include/linux/kexec.h              |  3 +++
>   kernel/kexec_file.c                | 10 ++++++++++
>   security/integrity/ima/ima_kexec.c |  3 +++
>   3 files changed, 16 insertions(+)
> 
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index f8413ea5c8c8..f3246e881ac8 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -362,6 +362,9 @@ struct kimage {
>   
>   	phys_addr_t ima_buffer_addr;
>   	size_t ima_buffer_size;
> +
> +	unsigned long ima_segment_index;
> +	bool is_ima_segment_index_set;
 >   #endif>
>   	/* Core ELF header buffer */
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 3eedb8c226ad..4ff3ba0f3e8e 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -764,6 +764,16 @@ static int kexec_calculate_store_digests(struct kimage *image)
>   		if (ksegment->kbuf == pi->purgatory_buf)
>   			continue;
>   
> +#ifdef CONFIG_IMA_KEXEC
> +		/*
> +		 * Skip the segment if ima_segment_index is set and matches
> +		 * the current index
> +		 */
> +		if (image->is_ima_segment_index_set &&
> +		    i == image->ima_segment_index)
> +			continue;
> +#endif
> +
>   		ret = crypto_shash_update(desc, ksegment->kbuf,
>   					  ksegment->bufsz);
>   		if (ret)
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index b60a902460e2..283860d20521 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -162,6 +162,7 @@ void ima_add_kexec_buffer(struct kimage *image)
>   	kbuf.buffer = kexec_buffer;
>   	kbuf.bufsz = kexec_buffer_size;
>   	kbuf.memsz = kexec_segment_size;
> +	image->is_ima_segment_index_set = false;
>   	ret = kexec_add_buffer(&kbuf);
>   	if (ret) {
>   		pr_err("Error passing over kexec measurement buffer.\n");
> @@ -172,6 +173,8 @@ void ima_add_kexec_buffer(struct kimage *image)
>   	image->ima_buffer_addr = kbuf.mem;
>   	image->ima_buffer_size = kexec_segment_size;
>   	image->ima_buffer = kexec_buffer;
> +	image->ima_segment_index = image->nr_segments - 1;
> +	image->is_ima_segment_index_set = true;
>   
>   	/*
>   	 * kexec owns kexec_buffer after kexec_add_buffer() is called

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
steven chen Jan. 29, 2025, 5:58 p.m. UTC | #2 
On 1/28/2025 7:23 AM, Stefan Berger wrote:
>
>
> On 1/24/25 5:55 PM, steven chen wrote:
>> kexec_calculate_store_digests() calculates and stores the digest of the
>> segment at kexec_file_load syscall where the IMA segment is also
>> allocated.  With this series, the IMA segment will be updated with the
>> measurement log at kexec soft reboot.  Therefore, it may fail digest
>
> ... log at kexec execute stage when the soft reboot is initiated.
>
>> verification in verify_sha256_digest() after kexec soft reboot into the
> > new Kernel.  Therefore, the digest calculation/verification of the IMA
>
> kernel
>
>> segment needs to be skipped.
>>
>> Skip IMA segment from calculating and storing digest in function
>> kexec_calculate_store_digests() so that it is not added to the
>> 'purgatory_sha_regions'.
>>
>> Since verify_sha256_digest() only verifies 'purgatory_sha_regions',
>> no change is needed in verify_sha256_digest() in this context.
>>
>> With this change, the IMA segment is not included in the digest
>> calculation, storage, and verification.
>>
>> Author: Tushar Sugandhi <tusharsu@linux.microsoft.com>
>> Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
>> Signed-off-by: steven chen <chenste@linux.microsoft.com>
>> ---
>>   include/linux/kexec.h              |  3 +++
>>   kernel/kexec_file.c                | 10 ++++++++++
>>   security/integrity/ima/ima_kexec.c |  3 +++
>>   3 files changed, 16 insertions(+)
>>
>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>> index f8413ea5c8c8..f3246e881ac8 100644
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -362,6 +362,9 @@ struct kimage {
>>         phys_addr_t ima_buffer_addr;
>>       size_t ima_buffer_size;
>> +
>> +    unsigned long ima_segment_index;
>> +    bool is_ima_segment_index_set;
> >   #endif>
>>       /* Core ELF header buffer */
>> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
>> index 3eedb8c226ad..4ff3ba0f3e8e 100644
>> --- a/kernel/kexec_file.c
>> +++ b/kernel/kexec_file.c
>> @@ -764,6 +764,16 @@ static int kexec_calculate_store_digests(struct 
>> kimage *image)
>>           if (ksegment->kbuf == pi->purgatory_buf)
>>               continue;
>>   +#ifdef CONFIG_IMA_KEXEC
>> +        /*
>> +         * Skip the segment if ima_segment_index is set and matches
>> +         * the current index
>> +         */
>> +        if (image->is_ima_segment_index_set &&
>> +            i == image->ima_segment_index)
>> +            continue;
>> +#endif
>> +
>>           ret = crypto_shash_update(desc, ksegment->kbuf,
>>                         ksegment->bufsz);
>>           if (ret)
>> diff --git a/security/integrity/ima/ima_kexec.c 
>> b/security/integrity/ima/ima_kexec.c
>> index b60a902460e2..283860d20521 100644
>> --- a/security/integrity/ima/ima_kexec.c
>> +++ b/security/integrity/ima/ima_kexec.c
>> @@ -162,6 +162,7 @@ void ima_add_kexec_buffer(struct kimage *image)
>>       kbuf.buffer = kexec_buffer;
>>       kbuf.bufsz = kexec_buffer_size;
>>       kbuf.memsz = kexec_segment_size;
>> +    image->is_ima_segment_index_set = false;
>>       ret = kexec_add_buffer(&kbuf);
>>       if (ret) {
>>           pr_err("Error passing over kexec measurement buffer.\n");
>> @@ -172,6 +173,8 @@ void ima_add_kexec_buffer(struct kimage *image)
>>       image->ima_buffer_addr = kbuf.mem;
>>       image->ima_buffer_size = kexec_segment_size;
>>       image->ima_buffer = kexec_buffer;
>> +    image->ima_segment_index = image->nr_segments - 1;
>> +    image->is_ima_segment_index_set = true;
>>         /*
>>        * kexec owns kexec_buffer after kexec_add_buffer() is called
>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>

Thanks. Will update in next release.
diff mbox series

Patch

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index f8413ea5c8c8..f3246e881ac8 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -362,6 +362,9 @@  struct kimage {
 
 	phys_addr_t ima_buffer_addr;
 	size_t ima_buffer_size;
+
+	unsigned long ima_segment_index;
+	bool is_ima_segment_index_set;
 #endif
 
 	/* Core ELF header buffer */
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 3eedb8c226ad..4ff3ba0f3e8e 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -764,6 +764,16 @@  static int kexec_calculate_store_digests(struct kimage *image)
 		if (ksegment->kbuf == pi->purgatory_buf)
 			continue;
 
+#ifdef CONFIG_IMA_KEXEC
+		/*
+		 * Skip the segment if ima_segment_index is set and matches
+		 * the current index
+		 */
+		if (image->is_ima_segment_index_set &&
+		    i == image->ima_segment_index)
+			continue;
+#endif
+
 		ret = crypto_shash_update(desc, ksegment->kbuf,
 					  ksegment->bufsz);
 		if (ret)
diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index b60a902460e2..283860d20521 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -162,6 +162,7 @@  void ima_add_kexec_buffer(struct kimage *image)
 	kbuf.buffer = kexec_buffer;
 	kbuf.bufsz = kexec_buffer_size;
 	kbuf.memsz = kexec_segment_size;
+	image->is_ima_segment_index_set = false;
 	ret = kexec_add_buffer(&kbuf);
 	if (ret) {
 		pr_err("Error passing over kexec measurement buffer.\n");
@@ -172,6 +173,8 @@  void ima_add_kexec_buffer(struct kimage *image)
 	image->ima_buffer_addr = kbuf.mem;
 	image->ima_buffer_size = kexec_segment_size;
 	image->ima_buffer = kexec_buffer;
+	image->ima_segment_index = image->nr_segments - 1;
+	image->is_ima_segment_index_set = true;
 
 	/*
 	 * kexec owns kexec_buffer after kexec_add_buffer() is called