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

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Message-ID: <Z/Sd+JdEbih7O48k@MiWiFi-R3L-srv>
Date: Tue, 8 Apr 2025 11:54:32 +0800
From: Baoquan He <bhe@...hat.com>
To: steven chen <chenste@...ux.microsoft.com>
Cc: zohar@...ux.ibm.com, stefanb@...ux.ibm.com,
	roberto.sassu@...weicloud.com, roberto.sassu@...wei.com,
	eric.snowberg@...cle.com, ebiederm@...ssion.com,
	paul@...l-moore.com, code@...icks.com, bauermann@...abnow.com,
	linux-integrity@...r.kernel.org, kexec@...ts.infradead.org,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org,
	madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
	James.Bottomley@...senpartnership.com, vgoyal@...hat.com,
	dyoung@...hat.com
Subject: Re: [PATCH v11 7/9] ima: verify if the segment size has changed

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@...hat.com>

> 
> Signed-off-by: steven chen <chenste@...ux.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
>