2023-11-06 12:49:48

by Steffen Eiden

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

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 <[email protected]>
---
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;
--
2.39.2

2023-11-06 12:50:44

by Claudio Imbrenda

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

On Mon, 6 Nov 2023 13:49:22 +0100
Steffen Eiden <[email protected]> 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 <[email protected]>

Reviewed-by: Claudio Imbrenda <[email protected]>

> ---
> 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;