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 <seiden@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20231106124922.3032370-1-seiden@linux.ibm.com
Message-Id: <20231106124922.3032370-1-seiden@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
index 144cd2e035909bceac10bd75e00ec9b7b721d6e5..42c9f77f8da0a00aa272e6875e8dbd30d7c3e54e 100644 (file)
--- 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;