[dm-devel] [RFC PATCH 2/3] dm verity: add support for IMA target update event

[Lakshmi Ramasubramanian]

Hi Thore,

On 1/6/2022 12:34 PM, Thore Sommer wrote:
> On first corruption the verity targets triggers a dm_target_update event.
> This allows other systems to check using IMA if the state of the device is
> still trustworthy via remote attestation.
In the patch description please state the existing problem (or, 
limitation in the existing implementation) and then describe how the 
proposed change addresses the issue.

> 
> Signed-off-by: Thore Sommer <public at thson.de>
> ---
>   drivers/md/dm-verity-target.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> index 80133aae0db3..09696e25bf1c 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -16,6 +16,7 @@
>   #include "dm-verity.h"
>   #include "dm-verity-fec.h"
>   #include "dm-verity-verify-sig.h"
> +#include "dm-ima.h"
>   #include <linux/module.h>
>   #include <linux/reboot.h>
>   #include <linux/scatterlist.h>
> @@ -218,10 +219,15 @@ static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
>   	char *envp[] = { verity_env, NULL };
>   	const char *type_str = "";
>   	struct mapped_device *md = dm_table_get_md(v->ti->table);
> +	int old_hash_failed = v->hash_failed;
>   
>   	/* Corruption should be visible in device status in all modes */
>   	v->hash_failed = 1;
>   
> +	/* Only remeasure on first failure */
> +	if (!old_hash_failed)
> +		dm_ima_measure_on_target_update(v->ti);
It is not obvious to me why the call to measure on target update is not 
done here immediately. Updating the comment to explain the logic would help.

thanks,
  -lakshmi

> +
>   	if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
>   		goto out;
>