[PATCH v5 4/8] ima: kexec: define functions to copy IMA log at soft boot

[Mimi Zohar]

Additional comments ...

> diff --git a/security/integrity/ima/ima_kexec.c
> b/security/integrity/ima/ima_kexec.c
> index ccb072617c2d..1d4d6c122d82 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -12,10 +12,14 @@
>  #include <linux/kexec.h>
>  #include <linux/of.h>
>  #include <linux/ima.h>
> +#include <linux/reboot.h>
> +#include <asm/page.h>
>  #include "ima.h"
>  
>  #ifdef CONFIG_IMA_KEXEC
>  static struct seq_file ima_kexec_file;
> +static void *ima_kexec_buffer;
> +static bool ima_kexec_update_registered;
>  
>  static void ima_reset_kexec_file(struct seq_file *sf)
>  {
> @@ -184,6 +188,48 @@ void ima_add_kexec_buffer(struct kimage *image)
>  	kexec_dprintk("kexec measurement buffer for the loaded kernel at
> 0x%lx.\n",
>  		      kbuf.mem);
>  }
> +
> +/*
> + * Called during kexec execute so that IMA can update the measurement list.
> + */
> +static int ima_update_kexec_buffer(struct notifier_block *self,
> +				   unsigned long action, void *data)
> +{
> +	return NOTIFY_OK;
> +}
> +
> +struct notifier_block update_buffer_nb = {

This should be defined as static.  update_buffer_nb should be prefixed with
'ima_'.

> +	.notifier_call = ima_update_kexec_buffer,
> +};
> +
> +/*
> + * Create a mapping for the source pages that contain the IMA buffer
> + * so we can update it later.
> + */
> +void ima_kexec_post_load(struct kimage *image)
> +{

In ima_alloc_kexec_file_buf(), the buffer is only re-allocated if the size
changes.  Here there doesn't seem to be way of detecting a size change.  At
least, add a comment here indicating that kexec 'load' may be called multiple
times.

Mimi

> +	if (ima_kexec_buffer) {
> +		kimage_unmap_segment(ima_kexec_buffer);
> +		ima_kexec_buffer = NULL;
> +	}
> +
> +	if (!image->ima_buffer_addr)
> +		return;
> +
> +	ima_kexec_buffer = kimage_map_segment(image,
> +					      image->ima_buffer_addr,
> +					      image->ima_buffer_size);
> +	if (!ima_kexec_buffer) {
> +		pr_err("%s: Could not map measurements buffer.\n", __func__);
> +		return;
> +	}
> +
> +	if (!ima_kexec_update_registered) {
> +		register_reboot_notifier(&update_buffer_nb);
> +		ima_kexec_update_registered = true;
> +	}
> +}
> +
>  #endif /* IMA_KEXEC */
>  
>  /*