On Fri, 2023-12-15 at 17:07 -0800, Tushar Sugandhi wrote:
> If the new measurements are added to the IMA log while it is being
> being copied to the kexec buffer during kexec 'execute', it can miss
> copying those new measurements to the kexec buffer, and the buffer can go
> out of sync with TPM PCRs. This could result in breaking the integrity
> of the measurements after the kexec soft reboot to the new Kernel.
>
> Add a check in the ima_add_template_entry() function not to measure
> events and return from the function early when 'suspend_ima_measurements'
> flag is set.
>
> This ensures the consistency of the IMA measurement list while copying
> them to the kexec buffer. When the 'suspend_ima_measurements' flag is
> set, any new measurements will be ignored until the flag is unset. This
> allows the buffer to be safely copied without worrying about concurrent
> modifications to the measurement list. This is crucial for maintaining
> the integrity of the measurements during a kexec soft reboot.
>
> Signed-off-by: Tushar Sugandhi <tusha...@linux.microsoft.com>
> ---
> security/integrity/ima/ima_queue.c | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/security/integrity/ima/ima_queue.c
> b/security/integrity/ima/ima_queue.c
> index cb9abc02a304..5946a26a2849 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -195,6 +195,19 @@ int ima_add_template_entry(struct ima_template_entry
> *entry, int violation,
> }
> }
>
> + /*
> + * suspend_ima_measurements will be set if the system is
> + * undergoing kexec soft boot to a new kernel.
> + * suspending measurements in this short window ensures the
> + * consistency of the IMA measurement list during copying
> + * of the kexec buffer.
> + */
> + if (atomic_read(&suspend_ima_measurements)) {
> + audit_cause = "measurements_suspended";
> + audit_info = 0;
> + goto out;
> + }
> +
> result = ima_add_digest_entry(entry,
> !IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE));
> if (result < 0) {
I assume you meant to include the suspend/resume code in "ima: kexec:
move ima log copy from kexec load to execute" in this patch.
--
thanks,
Mimi
