virtchnl: fix fake 1-elem arrays in structures allocated as `nents + 1`

There are five virtchnl structures, which are allocated and checked in
the code as `nents + 1`, meaning that they always have memory for one
excessive element regardless of their actual number. This comes from
that their sizeof() includes space for 1 element and then they get
allocated via struct_size() or its open-coded equivalents, passing
the actual number of elements.
Expand virtchnl_struct_size() to handle such structures and replace
those 1-elem arrays with proper flex ones. Also fix several places
which open-code %IAVF_VIRTCHNL_VF_RESOURCE_SIZE. Finally, let the
virtchnl_ether_addr_list size be computed automatically when there's
no enough space for the whole list, otherwise we have to open-code
reverse struct_size() logics.

Signed-off-by: Alexander Lobakin <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Tested-by: Rafal Romanowski <[e-mail]>
Signed-off-by: Tony Nguyen <[e-mail]>

drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c

···
 		goto err;
 	}
 
-	len = struct_size(vfres, vsi_res, num_vsis);
+	len = virtchnl_struct_size(vfres, vsi_res, num_vsis);
 	vfres = kzalloc(len, GFP_KERNEL);
 	if (!vfres) {
 		aq_ret = -ENOMEM;

drivers/net/ethernet/intel/iavf/iavf.h

···
 #define IAVF_MBPS_DIVISOR	125000 /* divisor to convert to Mbps */
 #define IAVF_MBPS_QUANTA	50
 
-#define IAVF_VIRTCHNL_VF_RESOURCE_SIZE (sizeof(struct virtchnl_vf_resource) + \
-					(IAVF_MAX_VF_VSI * \
-					 sizeof(struct virtchnl_vsi_resource)))
+#define IAVF_VIRTCHNL_VF_RESOURCE_SIZE					\
+	virtchnl_struct_size((struct virtchnl_vf_resource *)NULL,	\
+			     vsi_res, IAVF_MAX_VF_VSI)
 
 /* MAX_MSIX_Q_VECTORS of these are allocated,
  * but we only use one per queue-specific vector.

drivers/net/ethernet/intel/iavf/iavf_virtchnl.c

···
 	u16 len;
 	int err;
 
-	len = sizeof(struct virtchnl_vf_resource) +
-		IAVF_MAX_VF_VSI * sizeof(struct virtchnl_vsi_resource);
+	len = IAVF_VIRTCHNL_VF_RESOURCE_SIZE;
 	event.buf_len = len;
 	event.msg_buf = kzalloc(len, GFP_KERNEL);
 	if (!event.msg_buf)
···
 		return;
 	}
 	adapter->current_op = VIRTCHNL_OP_CONFIG_VSI_QUEUES;
-	len = struct_size(vqci, qpair, pairs);
+	len = virtchnl_struct_size(vqci, qpair, pairs);
 	vqci = kzalloc(len, GFP_KERNEL);
 	if (!vqci)
 		return;
···
 
 	q_vectors = adapter->num_msix_vectors - NONQ_VECS;
 
-	len = struct_size(vimi, vecmap, adapter->num_msix_vectors);
+	len = virtchnl_struct_size(vimi, vecmap, adapter->num_msix_vectors);
 	vimi = kzalloc(len, GFP_KERNEL);
 	if (!vimi)
 		return;
···
 	}
 	adapter->current_op = VIRTCHNL_OP_ADD_ETH_ADDR;
 
-	len = struct_size(veal, list, count);
+	len = virtchnl_struct_size(veal, list, count);
 	if (len > IAVF_MAX_AQ_BUF_SIZE) {
 		dev_warn(&adapter->pdev->dev, "Too many add MAC changes in one request\n");
-		count = (IAVF_MAX_AQ_BUF_SIZE -
-			 sizeof(struct virtchnl_ether_addr_list)) /
-			sizeof(struct virtchnl_ether_addr);
-		len = struct_size(veal, list, count);
+		while (len > IAVF_MAX_AQ_BUF_SIZE)
+			len = virtchnl_struct_size(veal, list, --count);
 		more = true;
 	}
 
···
 	}
 	adapter->current_op = VIRTCHNL_OP_DEL_ETH_ADDR;
 
-	len = struct_size(veal, list, count);
+	len = virtchnl_struct_size(veal, list, count);
 	if (len > IAVF_MAX_AQ_BUF_SIZE) {
 		dev_warn(&adapter->pdev->dev, "Too many delete MAC changes in one request\n");
-		count = (IAVF_MAX_AQ_BUF_SIZE -
-			 sizeof(struct virtchnl_ether_addr_list)) /
-			sizeof(struct virtchnl_ether_addr);
-		len = struct_size(veal, list, count);
+		while (len > IAVF_MAX_AQ_BUF_SIZE)
+			len = virtchnl_struct_size(veal, list, --count);
 		more = true;
 	}
 	veal = kzalloc(len, GFP_ATOMIC);
···
 
 		adapter->current_op = VIRTCHNL_OP_ADD_VLAN;
 
-		len = sizeof(*vvfl) + (count * sizeof(u16));
+		len = virtchnl_struct_size(vvfl, vlan_id, count);
 		if (len > IAVF_MAX_AQ_BUF_SIZE) {
 			dev_warn(&adapter->pdev->dev, "Too many add VLAN changes in one request\n");
-			count = (IAVF_MAX_AQ_BUF_SIZE - sizeof(*vvfl)) /
-				sizeof(u16);
-			len = sizeof(*vvfl) + (count * sizeof(u16));
+			while (len > IAVF_MAX_AQ_BUF_SIZE)
+				len = virtchnl_struct_size(vvfl, vlan_id,
+							   --count);
 			more = true;
 		}
 		vvfl = kzalloc(len, GFP_ATOMIC);
···
 
 		adapter->current_op = VIRTCHNL_OP_DEL_VLAN;
 
-		len = sizeof(*vvfl) + (count * sizeof(u16));
+		len = virtchnl_struct_size(vvfl, vlan_id, count);
 		if (len > IAVF_MAX_AQ_BUF_SIZE) {
 			dev_warn(&adapter->pdev->dev, "Too many delete VLAN changes in one request\n");
-			count = (IAVF_MAX_AQ_BUF_SIZE - sizeof(*vvfl)) /
-				sizeof(u16);
-			len = sizeof(*vvfl) + (count * sizeof(u16));
+			while (len > IAVF_MAX_AQ_BUF_SIZE)
+				len = virtchnl_struct_size(vvfl, vlan_id,
+							   --count);
 			more = true;
 		}
 		vvfl = kzalloc(len, GFP_ATOMIC);
···
 		}
 		break;
 	case VIRTCHNL_OP_GET_VF_RESOURCES: {
-		u16 len = sizeof(struct virtchnl_vf_resource) +
-			  IAVF_MAX_VF_VSI *
-			  sizeof(struct virtchnl_vsi_resource);
+		u16 len = IAVF_VIRTCHNL_VF_RESOURCE_SIZE;
+
 		memcpy(adapter->vf_res, msg, min(msglen, len));
 		iavf_validate_num_queues(adapter);
 		iavf_vf_parse_hw_config(&adapter->hw, adapter->vf_res);

drivers/net/ethernet/intel/ice/ice_virtchnl.c

···
 		goto err;
 	}
 
-	len = sizeof(struct virtchnl_vf_resource);
+	len = virtchnl_struct_size(vfres, vsi_res, 0);
 
 	vfres = kzalloc(len, GFP_KERNEL);
 	if (!vfres) {

include/linux/avf/virtchnl.h

···
 	u32 rss_key_size;
 	u32 rss_lut_size;
 
-	struct virtchnl_vsi_resource vsi_res[1];
+	struct virtchnl_vsi_resource vsi_res[];
 };
 
-VIRTCHNL_CHECK_STRUCT_LEN(36, virtchnl_vf_resource);
+VIRTCHNL_CHECK_STRUCT_LEN(20, virtchnl_vf_resource);
+#define virtchnl_vf_resource_LEGACY_SIZEOF	36
 
 /* VIRTCHNL_OP_CONFIG_TX_QUEUE
  * VF sends this message to set up parameters for one TX queue.
···
 	u16 vsi_id;
 	u16 num_queue_pairs;
 	u32 pad;
-	struct virtchnl_queue_pair_info qpair[1];
+	struct virtchnl_queue_pair_info qpair[];
 };
 
-VIRTCHNL_CHECK_STRUCT_LEN(72, virtchnl_vsi_queue_config_info);
+VIRTCHNL_CHECK_STRUCT_LEN(8, virtchnl_vsi_queue_config_info);
+#define virtchnl_vsi_queue_config_info_LEGACY_SIZEOF	72
 
 /* VIRTCHNL_OP_REQUEST_QUEUES
  * VF sends this message to request the PF to allocate additional queues to
···
 
 struct virtchnl_irq_map_info {
 	u16 num_vectors;
-	struct virtchnl_vector_map vecmap[1];
+	struct virtchnl_vector_map vecmap[];
 };
 
-VIRTCHNL_CHECK_STRUCT_LEN(14, virtchnl_irq_map_info);
+VIRTCHNL_CHECK_STRUCT_LEN(2, virtchnl_irq_map_info);
+#define virtchnl_irq_map_info_LEGACY_SIZEOF	14
 
 /* VIRTCHNL_OP_ENABLE_QUEUES
  * VIRTCHNL_OP_DISABLE_QUEUES
···
 struct virtchnl_ether_addr_list {
 	u16 vsi_id;
 	u16 num_elements;
-	struct virtchnl_ether_addr list[1];
+	struct virtchnl_ether_addr list[];
 };
 
-VIRTCHNL_CHECK_STRUCT_LEN(12, virtchnl_ether_addr_list);
+VIRTCHNL_CHECK_STRUCT_LEN(4, virtchnl_ether_addr_list);
+#define virtchnl_ether_addr_list_LEGACY_SIZEOF	12
 
 /* VIRTCHNL_OP_ADD_VLAN
  * VF sends this message to add one or more VLAN tag filters for receives.
···
 struct virtchnl_vlan_filter_list {
 	u16 vsi_id;
 	u16 num_elements;
-	u16 vlan_id[1];
+	u16 vlan_id[];
 };
 
-VIRTCHNL_CHECK_STRUCT_LEN(6, virtchnl_vlan_filter_list);
+VIRTCHNL_CHECK_STRUCT_LEN(4, virtchnl_vlan_filter_list);
+#define virtchnl_vlan_filter_list_LEGACY_SIZEOF	6
 
 /* This enum is used for all of the VIRTCHNL_VF_OFFLOAD_VLAN_V2_CAPS related
  * structures and opcodes.
···
 #define __vss_byone(p, member, count, old)				      \
 	(struct_size(p, member, count) + (old - 1 - struct_size(p, member, 0)))
 
+#define __vss_full(p, member, count, old)				      \
+	(struct_size(p, member, count) + (old - struct_size(p, member, 0)))
+
 #define __vss(type, func, p, member, count)		\
 	struct type: func(p, member, count, type##_LEGACY_SIZEOF)
 
 #define virtchnl_struct_size(p, m, c)					      \
 	_Generic(*p,							      \
+		 __vss(virtchnl_vf_resource, __vss_full, p, m, c),	      \
+		 __vss(virtchnl_vsi_queue_config_info, __vss_full, p, m, c),  \
+		 __vss(virtchnl_irq_map_info, __vss_full, p, m, c),	      \
+		 __vss(virtchnl_ether_addr_list, __vss_full, p, m, c),	      \
+		 __vss(virtchnl_vlan_filter_list, __vss_full, p, m, c),	      \
 		 __vss(virtchnl_rss_key, __vss_byone, p, m, c),		      \
 		 __vss(virtchnl_rss_lut, __vss_byone, p, m, c))
 
···
 		valid_len = sizeof(struct virtchnl_rxq_info);
 		break;
 	case VIRTCHNL_OP_CONFIG_VSI_QUEUES:
-		valid_len = sizeof(struct virtchnl_vsi_queue_config_info);
+		valid_len = virtchnl_vsi_queue_config_info_LEGACY_SIZEOF;
 		if (msglen >= valid_len) {
 			struct virtchnl_vsi_queue_config_info *vqc =
 			    (struct virtchnl_vsi_queue_config_info *)msg;
-			valid_len += (vqc->num_queue_pairs *
-				      sizeof(struct
-					     virtchnl_queue_pair_info));
+			valid_len = virtchnl_struct_size(vqc, qpair,
+							 vqc->num_queue_pairs);
 			if (vqc->num_queue_pairs == 0)
 				err_msg_format = true;
 		}
 		break;
 	case VIRTCHNL_OP_CONFIG_IRQ_MAP:
-		valid_len = sizeof(struct virtchnl_irq_map_info);
+		valid_len = virtchnl_irq_map_info_LEGACY_SIZEOF;
 		if (msglen >= valid_len) {
 			struct virtchnl_irq_map_info *vimi =
 			    (struct virtchnl_irq_map_info *)msg;
-			valid_len += (vimi->num_vectors *
-				      sizeof(struct virtchnl_vector_map));
+			valid_len = virtchnl_struct_size(vimi, vecmap,
+							 vimi->num_vectors);
 			if (vimi->num_vectors == 0)
 				err_msg_format = true;
 		}
···
 		break;
 	case VIRTCHNL_OP_ADD_ETH_ADDR:
 	case VIRTCHNL_OP_DEL_ETH_ADDR:
-		valid_len = sizeof(struct virtchnl_ether_addr_list);
+		valid_len = virtchnl_ether_addr_list_LEGACY_SIZEOF;
 		if (msglen >= valid_len) {
 			struct virtchnl_ether_addr_list *veal =
 			    (struct virtchnl_ether_addr_list *)msg;
-			valid_len += veal->num_elements *
-			    sizeof(struct virtchnl_ether_addr);
+			valid_len = virtchnl_struct_size(veal, list,
+							 veal->num_elements);
 			if (veal->num_elements == 0)
 				err_msg_format = true;
 		}
 		break;
 	case VIRTCHNL_OP_ADD_VLAN:
 	case VIRTCHNL_OP_DEL_VLAN:
-		valid_len = sizeof(struct virtchnl_vlan_filter_list);
+		valid_len = virtchnl_vlan_filter_list_LEGACY_SIZEOF;
 		if (msglen >= valid_len) {
 			struct virtchnl_vlan_filter_list *vfl =
 			    (struct virtchnl_vlan_filter_list *)msg;
-			valid_len += vfl->num_elements * sizeof(u16);
+			valid_len = virtchnl_struct_size(vfl, vlan_id,
+							 vfl->num_elements);
 			if (vfl->num_elements == 0)
 				err_msg_format = true;
 		}