Re: [PATCH v4 4/7] ima: kexec: move ima log copy from kexec load to execute

[Mimi Zohar <zohar@linux.ibm.com>]

On Mon, 2024-01-22 at 10:38 -0800, Tushar Sugandhi wrote:
> ima_dump_measurement_list() is called during kexec 'load', which may
> result in loss of IMA measurements during kexec soft reboot.  It needs
> to be called during kexec 'execute'.
> 
> The below changes need to be part of the same patch to ensure this
> patch series remains bisect-safe by ensuring the IMA log gets copied over
> during kexec soft reboot both before and after this patch.
> 
> Implement ima_update_kexec_buffer() to be called during kexec 'execute'.
> Move ima_dump_measurement_list() from ima_add_kexec_buffer() to
> ima_update_kexec_buffer().  Make the necessary variables local static to
> the file, so that they are accessible during both kexec 'load' - where
> the memory is allocated and mapped to a segment in the new Kernel, and
> during 'execute' - where the IMA log gets copied over.
> 
> Implement kimage_file_post_load() and ima_kexec_post_load() to be invoked
> after the new Kernel image has been loaded for kexec.
> ima_kexec_post_load() will map the IMA buffer to a segment in the newly
> loaded Kernel.  It will also register the reboot notifier_block to trigger
> ima_update_kexec_buffer() at exec 'execute'.

This defines two new IMA hooks - ima_kexec_post_load() and
ima_update_kexec_buffer().  They shouldn't be hidden here in the move of copying
the measurement list from kexec load to execute.

If "ima_update_kexec_buffer()" was initially defined as a stub function, the
infrastructure could be set up ahead of time.  This patch could then be limited
to just moving the copy from kexec "load" to "execute", by replacing the stub
function with the real function.

> Modify kexec_file_load() syscall to call kimage_file_post_load() after the
> image has been loaded and prepared for kexec.  Call it only on kexec soft
> reboot and not for KEXEC_FILE_ON_CRASH.

-- 
thanks,

Mimi