net/sched: cls_u32: Use struct_size() helper

Make use of the struct_size() helper, in multiple places, instead
of an open-coded version in order to avoid any potential type
mistakes and protect against potential integer overflows.

Also, remove unnecessary object identifier size.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_u32.c

@@ -852,9 +852,6 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
 	u32 htid, flags = 0;
 	size_t sel_size;
 	int err;
-#ifdef CONFIG_CLS_U32_PERF
-	size_t size;
-#endif
 
 	if (!opt) {
 		if (handle) {
@@ -1022,15 +1019,15 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
 		goto erridr;
 	}
 
-	n = kzalloc(offsetof(typeof(*n), sel) + sel_size, GFP_KERNEL);
+	n = kzalloc(struct_size(n, sel.keys, s->nkeys), GFP_KERNEL);
 	if (n == NULL) {
 		err = -ENOBUFS;
 		goto erridr;
 	}
 
 #ifdef CONFIG_CLS_U32_PERF
-	size = sizeof(struct tc_u32_pcnt) + s->nkeys * sizeof(u64);
-	n->pf = __alloc_percpu(size, __alignof__(struct tc_u32_pcnt));
+	n->pf = __alloc_percpu(struct_size(n->pf, kcnts, s->nkeys),
+			       __alignof__(struct tc_u32_pcnt));
 	if (!n->pf) {
 		err = -ENOBUFS;
 		goto errfree;
@@ -1294,8 +1291,7 @@ static int u32_dump(struct net *net, struct tcf_proto *tp, void *fh,
 		int cpu;
 #endif
 
-		if (nla_put(skb, TCA_U32_SEL,
-			    sizeof(n->sel) + n->sel.nkeys*sizeof(struct tc_u32_key),
+		if (nla_put(skb, TCA_U32_SEL, struct_size(&n->sel, keys, n->sel.nkeys),
 			    &n->sel))
 			goto nla_put_failure;
 
@@ -1345,9 +1341,7 @@ static int u32_dump(struct net *net, struct tcf_proto *tp, void *fh,
 				goto nla_put_failure;
 		}
 #ifdef CONFIG_CLS_U32_PERF
-		gpf = kzalloc(sizeof(struct tc_u32_pcnt) +
-			      n->sel.nkeys * sizeof(u64),
-			      GFP_KERNEL);
+		gpf = kzalloc(struct_size(gpf, kcnts, n->sel.nkeys), GFP_KERNEL);
 		if (!gpf)
 			goto nla_put_failure;
 
@@ -1361,9 +1355,7 @@ static int u32_dump(struct net *net, struct tcf_proto *tp, void *fh,
 				gpf->kcnts[i] += pf->kcnts[i];
 		}
 
-		if (nla_put_64bit(skb, TCA_U32_PCNT,
-				  sizeof(struct tc_u32_pcnt) +
-				  n->sel.nkeys * sizeof(u64),
+		if (nla_put_64bit(skb, TCA_U32_PCNT, struct_size(gpf, kcnts, n->sel.nkeys),
 				  gpf, TCA_U32_PAD)) {
 			kfree(gpf);
 			goto nla_put_failure;