[PATCH v11 8/9] ima: make the kexec extra memory configurable

[Baoquan He]

On 04/02/25 at 05:47am, steven chen wrote:
> The extra memory allocated for carrying the IMA measurement list across
> kexec is hard-coded as half a PAGE.  Make it configurable.
> 
> Define a Kconfig option, IMA_KEXEC_EXTRA_MEMORY_KB, to configure the
> extra memory (in kb) to be allocated for IMA measurements added during
> kexec soft reboot.  Ensure the default value of the option is set such
> that extra half a page of memory for additional measurements is allocated
> for the additional measurements.
> 
> Update ima_add_kexec_buffer() function to allocate memory based on the
> Kconfig option value, rather than the currently hard-coded one.
> 
> Suggested-by: Stefan Berger <stefanb at linux.ibm.com>
> Signed-off-by: Tushar Sugandhi <tusharsu at linux.microsoft.com>
> Signed-off-by: steven chen <chenste at linux.microsoft.com>
> Reviewed-by: Stefan Berger <stefanb at linux.ibm.com>
> Reviewed-by: Mimi Zohar <zohar at linux.ibm.com>
> ---
>  security/integrity/ima/Kconfig     | 10 ++++++++++
>  security/integrity/ima/ima_kexec.c | 16 +++++++++++-----
>  2 files changed, 21 insertions(+), 5 deletions(-)
> 
> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> index 475c32615006..d73c96c3c1c9 100644
> --- a/security/integrity/ima/Kconfig
> +++ b/security/integrity/ima/Kconfig
> @@ -321,4 +321,14 @@ config IMA_DISABLE_HTABLE
>  	help
>  	   This option disables htable to allow measurement of duplicate records.
>  
> +config IMA_KEXEC_EXTRA_MEMORY_KB
> +	int "Extra memory for IMA measurements added during kexec soft reboot"
> +	depends on IMA_KEXEC
> +	default 0

Usually a new Kconfig item which accepts a range should define the range
boundary, otherwise it's not clear to people how large or how small it
can be set. For example, can I set it as value of 1<<40? We should at
least estimate a possible upper limit for it for other people's
reference. My personal opinion.

The rest looks good to me.


> +	help
> +	  IMA_KEXEC_EXTRA_MEMORY_KB determines the extra memory to be
> +	  allocated (in kb) for IMA measurements added during kexec soft reboot.
> +	  If set to the default value of 0, an extra half page of memory for those
> +	  additional measurements will be allocated.
> +
>  endif
...snip...