net: qed: Fix memcpy() overflow of qed_dcbx_params()

The source (&dcbx_info->operational.params) and dest
(&p_hwfn->p_dcbx_info->set.config.params) are both struct qed_dcbx_params
(560 bytes), not struct qed_dcbx_admin_params (564 bytes), which is used
as the memcpy() size.

However it seems that struct qed_dcbx_operational_params
(dcbx_info->operational)'s layout matches struct qed_dcbx_admin_params
(p_hwfn->p_dcbx_info->set.config)'s 4 byte difference (3 padding, 1 byte
for "valid").

On the assumption that the size is wrong (rather than the source structure
type), adjust the memcpy() size argument to be 4 bytes smaller and add
a BUILD_BUG_ON() to validate any changes to the structure sizes.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qed/qed_dcbx.c

@@ -1266,9 +1266,11 @@ int qed_dcbx_get_config_params(struct qed_hwfn *p_hwfn,
 		p_hwfn->p_dcbx_info->set.ver_num |= DCBX_CONFIG_VERSION_STATIC;
 
 	p_hwfn->p_dcbx_info->set.enabled = dcbx_info->operational.enabled;
+	BUILD_BUG_ON(sizeof(dcbx_info->operational.params) !=
+		     sizeof(p_hwfn->p_dcbx_info->set.config.params));
 	memcpy(&p_hwfn->p_dcbx_info->set.config.params,
 	       &dcbx_info->operational.params,
-	       sizeof(struct qed_dcbx_admin_params));
+	       sizeof(p_hwfn->p_dcbx_info->set.config.params));
 	p_hwfn->p_dcbx_info->set.config.valid = true;
 
 	memcpy(params, &p_hwfn->p_dcbx_info->set, sizeof(struct qed_dcbx_set));