netdev - [PATCH] datapath: Avoid using stack larger than 1024.

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Date:   Tue, 27 Jun 2017 02:20:49 -0700
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     netdev@...r.kernel.org
Cc:     Tonghao Zhang <xiangxia.m.yue@...il.com>
Subject: [PATCH] datapath: Avoid using stack larger than 1024.

When compiling OvS-master on 4.4.0-81 kernel,
there is a warning:

    CC [M]  /root/ovs/datapath/linux/datapath.o
    /root/ovs/datapath/linux/datapath.c: In function
    ‘ovs_flow_cmd_set’:
    /root/ovs/datapath/linux/datapath.c:1221:1: warning:
    the frame size of 1040 bytes is larger than 1024 bytes
    [-Wframe-larger-than=]

This patch use kmalloc to malloc mem for sw_flow_mask and
avoid using stack.

Signed-off-by: Tonghao Zhang <xiangxia.m.yue@...il.com>
---
 net/openvswitch/datapath.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index c85029c..da8cd68 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1107,7 +1107,7 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
 	struct ovs_header *ovs_header = info->userhdr;
 	struct sw_flow_key key;
 	struct sw_flow *flow;
-	struct sw_flow_mask mask;
+	struct sw_flow_mask *mask;
 	struct sk_buff *reply = NULL;
 	struct datapath *dp;
 	struct sw_flow_actions *old_acts = NULL, *acts = NULL;
@@ -1120,7 +1120,11 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
 
 	ufid_present = ovs_nla_get_ufid(&sfid, a[OVS_FLOW_ATTR_UFID], log);
 	if (a[OVS_FLOW_ATTR_KEY]) {
-		ovs_match_init(&match, &key, true, &mask);
+		mask = kmalloc(sizeof(struct sw_flow_mask), GFP_KERNEL);
+		if (!mask)
+			return -ENOMEM;
+
+		ovs_match_init(&match, &key, true, mask);
 		error = ovs_nla_get_match(net, &match, a[OVS_FLOW_ATTR_KEY],
 					  a[OVS_FLOW_ATTR_MASK], log);
 	} else if (!ufid_present) {
@@ -1141,7 +1145,7 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
 		}
 
 		acts = get_flow_actions(net, a[OVS_FLOW_ATTR_ACTIONS], &key,
-					&mask, log);
+					mask, log);
 		if (IS_ERR(acts)) {
 			error = PTR_ERR(acts);
 			goto error;
@@ -1216,6 +1220,7 @@ err_unlock_ovs:
 err_kfree_acts:
 	ovs_nla_free_flow_actions(acts);
 error:
+	kfree(mask);
 	return error;
 }
 
-- 
1.8.3.1