drm/amdgpu: Fix shared buff copy to user

[ Upstream commit 2dcf82a ]

ta if invoke node buffer
|-------- ta type ----------|
|--------  ta id  ----------|
|-------- cmd  id ----------|
|------ shared buf len -----|
|------ shared buffer ------|

ta if invoke node buffer is as above, copy shared buffer data to correct location

Signed-off-by: Stanley.Yang <Stanley.Yang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/amd/amdgpu/amdgpu_psp_ta.c

@@ -362,7 +362,7 @@ static ssize_t ta_if_invoke_debugfs_write(struct file *fp, const char *buf, size
 		}
 	}
 
-	if (copy_to_user((char *)buf, context->mem_context.shared_buf, shared_buf_len))
+	if (copy_to_user((char *)&buf[copy_pos], context->mem_context.shared_buf, shared_buf_len))
 		ret = -EFAULT;
 
 err_free_shared_buf: