qed: Prevent stack corruption on MFW interaction

Driver uses a union for copying data to & from management firmware
when interacting with it.
Problem is that the function always copies sizeof(union) while commit
2edbff8dcb5d ("qed: Learn resources from management firmware") is casting
a union elements which is of smaller size [24-byte instead of 88-bytes].

Also, the union contains some inappropriate elements which increase its
size [should have been 32-bytes]. While this shouldn't corrupt other
PF messages to the MFW [as management firmware enforces permissions so
that each PF is allowed to write only to its own mailbox] we fix this
here as well.

Fixes: 2edbff8dcb5d ("qed: Learn resources from management firmware")
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qlogic/qed/qed_hsi.h

@@ -8581,7 +8581,6 @@ union drv_union_data {
 	struct drv_version_stc drv_version;
 
 	struct lan_stats_stc lan_stats;
-	u64 reserved_stats[11];
 	struct ocbb_data_stc ocbb_info;
 	struct temperature_status_stc temp_info;
 	struct resource_info resource;

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

@@ -1697,19 +1697,27 @@ int qed_mcp_get_resc_info(struct qed_hwfn *p_hwfn,
 			  u32 *p_mcp_resp, u32 *p_mcp_param)
 {
 	struct qed_mcp_mb_params mb_params;
-	union drv_union_data *p_union_data;
+	union drv_union_data union_data;
 	int rc;
 
 	memset(&mb_params, 0, sizeof(mb_params));
+	memset(&union_data, 0, sizeof(union_data));
 	mb_params.cmd = DRV_MSG_GET_RESOURCE_ALLOC_MSG;
 	mb_params.param = QED_RESC_ALLOC_VERSION;
-	p_union_data = (union drv_union_data *)p_resc_info;
-	mb_params.p_data_src = p_union_data;
-	mb_params.p_data_dst = p_union_data;
+
+	/* Need to have a sufficient large struct, as the cmd_and_union
+	 * is going to do memcpy from and to it.
+	 */
+	memcpy(&union_data.resource, p_resc_info, sizeof(*p_resc_info));
+
+	mb_params.p_data_src = &union_data;
+	mb_params.p_data_dst = &union_data;
 	rc = qed_mcp_cmd_and_union(p_hwfn, p_ptt, &mb_params);
 	if (rc)
 		return rc;
 
+	/* Copy the data back */
+	memcpy(p_resc_info, &union_data.resource, sizeof(*p_resc_info));
 	*p_mcp_resp = mb_params.mcp_resp;
 	*p_mcp_param = mb_params.mcp_param;