net/sched: cls_flower: allocate mask dynamically in fl_change()

Recent changes (especially 05cd271f ("cls_flower: Support multiple
masks per priority")) in the fl_flow_mask structure grow it and its
current size e.g. on x86_64 with defconfig is 760 bytes and more than
1024 bytes with some debug options enabled. Prior the mentioned commit
its size was 176 bytes (using defconfig on x86_64).
With regard to this fact it's reasonable to allocate this structure
dynamically in fl_change() to reduce its stack size.

v2:
- use kzalloc() instead of kcalloc()

Fixes: 05cd271f ("cls_flower: Support multiple masks per priority")
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Paul Blakey <paulb@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_flower.c

@@ -1290,17 +1290,23 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 	struct cls_fl_head *head = rtnl_dereference(tp->root);
 	struct cls_fl_filter *fold = *arg;
 	struct cls_fl_filter *fnew;
+	struct fl_flow_mask *mask;
 	struct nlattr **tb;
-	struct fl_flow_mask mask = {};
 	int err;
 
 	if (!tca[TCA_OPTIONS])
 		return -EINVAL;
 
-	tb = kcalloc(TCA_FLOWER_MAX + 1, sizeof(struct nlattr *), GFP_KERNEL);
-	if (!tb)
+	mask = kzalloc(sizeof(struct fl_flow_mask), GFP_KERNEL);
+	if (!mask)
 		return -ENOBUFS;
 
+	tb = kcalloc(TCA_FLOWER_MAX + 1, sizeof(struct nlattr *), GFP_KERNEL);
+	if (!tb) {
+		err = -ENOBUFS;
+		goto errout_mask_alloc;
+	}
+
 	err = nla_parse_nested(tb, TCA_FLOWER_MAX, tca[TCA_OPTIONS],
 			       fl_policy, NULL);
 	if (err < 0)
@@ -1343,12 +1349,12 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 		}
 	}
 
-	err = fl_set_parms(net, tp, fnew, &mask, base, tb, tca[TCA_RATE], ovr,
+	err = fl_set_parms(net, tp, fnew, mask, base, tb, tca[TCA_RATE], ovr,
 			   tp->chain->tmplt_priv, extack);
 	if (err)
 		goto errout_idr;
 
-	err = fl_check_assign_mask(head, fnew, fold, &mask);
+	err = fl_check_assign_mask(head, fnew, fold, mask);
 	if (err)
 		goto errout_idr;
 
@@ -1392,6 +1398,7 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 	}
 
 	kfree(tb);
+	kfree(mask);
 	return 0;
 
 errout_mask:
@@ -1405,6 +1412,8 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 	kfree(fnew);
 errout_tb:
 	kfree(tb);
+errout_mask_alloc:
+	kfree(mask);
 	return err;
 }