Re: [PATCH v1 1/1] s390/uvdevice: Report additional-data length for attestation

Claudio Imbrenda
2023-11-06T12:50:20Z

On Mon, 6 Nov 2023 13:49:22 +0100
Steffen Eiden <seiden@linux.ibm.com> wrote:

> Additional data length in the attestation request is an in/out variable.
> Software provides the capacity of the buffer. Upon successful request,
> firmware reports the actual bytes written to the additional data in that
> field. This information is lost, as the length field was not copied back
> to userspace before. Attestation might fail, if user space did not
> specify the exact amount of needed bytes required, as this length is
> part of the attestation measurement.
>
> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
> drivers/s390/char/uvdevice.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
> index 144cd2e03590..42c9f77f8da0 100644
> --- a/drivers/s390/char/uvdevice.c
> +++ b/drivers/s390/char/uvdevice.c
> @@ -109,6 +109,7 @@ static int uvio_copy_attest_result_to_user(struct uv_cb_attest *uvcb_attest,
> struct uvio_attest *uvio_attest)
> {
> struct uvio_attest __user *user_uvio_attest = (void __user *)uv_ioctl->argument_addr;
> + u32 __user *user_buf_add_len = (u32 __user *)&user_uvio_attest->add_data_len;
> void __user *user_buf_add = (void __user *)uvio_attest->add_data_addr;
> void __user *user_buf_meas = (void __user *)uvio_attest->meas_addr;
> void __user *user_buf_uid = &user_uvio_attest->config_uid;
> @@ -117,6 +118,8 @@ static int uvio_copy_attest_result_to_user(struct uv_cb_attest *uvcb_attest,
> return -EFAULT;
> if (add_data && copy_to_user(user_buf_add, add_data, uvio_attest->add_data_len))
> return -EFAULT;
> + if (put_user(uvio_attest->add_data_len, user_buf_add_len))
> + return -EFAULT;
> if (copy_to_user(user_buf_uid, uvcb_attest->config_uid, sizeof(uvcb_attest->config_uid)))
> return -EFAULT;
> return 0;