[PATCH 1/2] test: dm: virtio_rng: Update virtio-rng test

[Andre Przywara]

Hi Kavin,

On 2/17/26 14:29, Kavin Gunasekara wrote:
> The virtio-rng test to verify effective handling of oversized return
> buffers checks that an (undocumented) error is raised, instead of the
> real concern, which is the surrounding buffer integrity following a rng
> function call.
> Update the test to check that the other contents of a buffer remain
> unchanged instead of looking for an error code.
> 
> Signed-off-by: Kavin Gunasekara <kavin.gunasekara at arm.com>
> ---
>   test/dm/virtio_rng.c | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/test/dm/virtio_rng.c b/test/dm/virtio_rng.c
> index e404b08484e..7c3dd50ef3e 100644
> --- a/test/dm/virtio_rng.c
> +++ b/test/dm/virtio_rng.c
> @@ -19,12 +19,19 @@ struct virtio_rng_priv {
>   	struct virtqueue *rng_vq;
>   };
>   
> +#define BUFFER_SIZE 16
> +#define CANARY "CANARYCANARYCANARYCANARY"
> +
>   /* Test the virtio-rng driver validates the used size */
>   static int dm_test_virtio_rng_check_len(struct unit_test_state *uts)
>   {
>   	struct udevice *bus, *dev;
>   	struct virtio_rng_priv *priv;
> -	u8 buffer[16];
> +	u8 buffer[BUFFER_SIZE + sizeof(CANARY)];
> +
> +	/* write known data to buffer */
> +	memset(buffer, 0xaa, sizeof(buffer));

I don't think it makes much sense to fill the whole buffer here, only to 
overwrite the last part in the next line. We should not be that paranoid ;-)

The rest looks alright.

Cheers,
Andre

> +	memcpy(buffer + BUFFER_SIZE, CANARY, sizeof(CANARY));
>   
>   	/* check probe success */
>   	ut_assertok(uclass_first_device_err(UCLASS_VIRTIO, &bus));
> @@ -44,7 +51,10 @@ static int dm_test_virtio_rng_check_len(struct unit_test_state *uts)
>   	priv->rng_vq->vring.used->ring[0].len = U32_MAX;
>   
>   	/* check the driver gracefully handles the error */
> -	ut_asserteq(-EIO, dm_rng_read(dev, buffer, sizeof(buffer)));
> +	dm_rng_read(dev, buffer, BUFFER_SIZE);
> +
> +	/* check for the canary bytes behind the real buffer */
> +	ut_asserteq_mem(buffer + BUFFER_SIZE, CANARY, sizeof(CANARY));
>   
>   	return 0;
>   }