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

[steven chen]

On 4/10/2025 2:54 AM, Baoquan He wrote:
> 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@xxxxxxxxxxxxx>
> > Signed-off-by: Tushar Sugandhi <tusharsu@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: steven chen <chenste@xxxxxxxxxxxxxxxxxxx>
> > Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> > Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> > ---
> >   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.

Hi Baoquan,

How about I set range 2-40? Default set as 2, same as the fixed setting.

Thanks,

Steven

> 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...