drm/amdgpu: fix out of bounds write

Size can be any value and is user controlled resulting in overwriting the
40 byte array wr_buf with an arbitrary length of data from buf.

Signed-off-by: Thelford Williams <tdwilliamsiv@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -263,7 +263,7 @@ static ssize_t dp_link_settings_write(struct file *f, const char __user *buf,
 	if (!wr_buf)
 		return -ENOSPC;
 
-	if (parse_write_buffer_into_params(wr_buf, size,
+	if (parse_write_buffer_into_params(wr_buf, wr_buf_size,
 					   (long *)param, buf,
 					   max_param_num,
 					   &param_nums)) {