[v11] ima: kexec: measure events between kexec load and execute

[PATCH v11 7/9] ima: verify if the segment size has changed

Posted by steven chen 1 month, 1 week ago

kexec 'load' may be called multiple times. Free and realloc the buffer
only if the segment_size is changed from the previous kexec 'load' call.

Signed-off-by: steven chen <chenste@linux.microsoft.com>
---
 security/integrity/ima/ima_kexec.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 5c3b3e0b2186..ed867734ee70 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -33,6 +33,14 @@ static void ima_free_kexec_file_buf(struct seq_file *sf)
 
 static int ima_alloc_kexec_file_buf(size_t segment_size)
 {
+	/*
+	 * kexec 'load' may be called multiple times.
+	 * Free and realloc the buffer only if the segment_size is
+	 * changed from the previous kexec 'load' call.
+	 */
+	if (ima_kexec_file.buf && ima_kexec_file.size == segment_size)
+		goto out;
+
 	ima_free_kexec_file_buf(&ima_kexec_file);
 
 	/* segment size can't change between kexec load and execute */
@@ -41,6 +49,8 @@ static int ima_alloc_kexec_file_buf(size_t segment_size)
 		return -ENOMEM;
 
 	ima_kexec_file.size = segment_size;
+
+out:
 	ima_kexec_file.read_pos = 0;
 	ima_kexec_file.count = sizeof(struct ima_kexec_hdr);	/* reserved space */
 
-- 
2.25.1

Re: [PATCH v11 7/9] ima: verify if the segment size has changed

Posted by Mimi Zohar 1 month ago

On Wed, 2025-04-02 at 05:47 -0700, steven chen wrote:
> kexec 'load' may be called multiple times. Free and realloc the buffer
> only if the segment_size is changed from the previous kexec 'load' call.
> 
> Signed-off-by: steven chen <chenste@linux.microsoft.com>

Thanks, Steven.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Re: [PATCH v11 7/9] ima: verify if the segment size has changed

Posted by Baoquan He 1 month ago

On 04/02/25 at 05:47am, steven chen wrote:
> kexec 'load' may be called multiple times. Free and realloc the buffer
> only if the segment_size is changed from the previous kexec 'load' call.

This is a great example demonstrating how patch is nicely split. A
reasonable unit including reasonable code change and log.

Acked-by: Baoquan He <bhe@redhat.com>

> 
> Signed-off-by: steven chen <chenste@linux.microsoft.com>
> ---
>  security/integrity/ima/ima_kexec.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 5c3b3e0b2186..ed867734ee70 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -33,6 +33,14 @@ static void ima_free_kexec_file_buf(struct seq_file *sf)
>  
>  static int ima_alloc_kexec_file_buf(size_t segment_size)
>  {
> +	/*
> +	 * kexec 'load' may be called multiple times.
> +	 * Free and realloc the buffer only if the segment_size is
> +	 * changed from the previous kexec 'load' call.
> +	 */
> +	if (ima_kexec_file.buf && ima_kexec_file.size == segment_size)
> +		goto out;
> +
>  	ima_free_kexec_file_buf(&ima_kexec_file);
>  
>  	/* segment size can't change between kexec load and execute */
> @@ -41,6 +49,8 @@ static int ima_alloc_kexec_file_buf(size_t segment_size)
>  		return -ENOMEM;
>  
>  	ima_kexec_file.size = segment_size;
> +
> +out:
>  	ima_kexec_file.read_pos = 0;
>  	ima_kexec_file.count = sizeof(struct ima_kexec_hdr);	/* reserved space */
>  
> -- 
> 2.25.1
>