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 factors out match-init and action-copy to avoid
"Wframe-larger-than=1024" warning. Because mask is only
used to get actions, we new a function to save some
stack space.

Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 58 insertions, 23 deletions

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index d772e9a4b4f8..45fe8c8a884d 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1090,6 +1090,58 @@ static struct sw_flow_actions *get_flow_actions(struct net *net,
         return acts;
 }
 
+/* Factor out match-init and action-copy to avoid
+ * "Wframe-larger-than=1024" warning. Because mask is only
+ * used to get actions, we new a function to save some
+ * stack space.
+ *
+ * If there are not key and action attrs, we return 0
+ * directly. In the case, the caller will also not use the
+ * match as before. If there is action attr, we try to get
+ * actions and save them to *acts. Before returning from
+ * the function, we reset the match->mask pointer. Because
+ * we should not to return match object with dangling reference
+ * to mask.
+ * */
+static int ovs_nla_init_match_and_action(struct net *net,
+                                         struct sw_flow_match *match,
+                                         struct sw_flow_key *key,
+                                         struct nlattr **a,
+                                         struct sw_flow_actions **acts,
+                                         bool log)
+{
+        struct sw_flow_mask mask;
+        int error = 0;
+
+        if (a[OVS_FLOW_ATTR_KEY]) {
+                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);
+                if (error)
+                        goto error;
+        }
+
+        if (a[OVS_FLOW_ATTR_ACTIONS]) {
+                if (!a[OVS_FLOW_ATTR_KEY]) {
+                        OVS_NLERR(log,
+                                  "Flow key attribute not present in set flow.");
+                        return -EINVAL;
+                }
+
+                *acts = get_flow_actions(net, a[OVS_FLOW_ATTR_ACTIONS], key,
+                                         &mask, log);
+                if (IS_ERR(*acts)) {
+                        error = PTR_ERR(*acts);
+                        goto error;
+                }
+        }
+
+        /* On success, error is 0. */
+error:
+        match->mask = NULL;
+        return error;
+}
+
 static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
 {
         struct net *net = sock_net(skb->sk);
@@ -1097,7 +1149,6 @@ 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 sk_buff *reply = NULL;
         struct datapath *dp;
         struct sw_flow_actions *old_acts = NULL, *acts = NULL;
@@ -1109,34 +1160,18 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
         bool ufid_present;
 
         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);
-                error = ovs_nla_get_match(net, &match, a[OVS_FLOW_ATTR_KEY],
-                                          a[OVS_FLOW_ATTR_MASK], log);
-        } else if (!ufid_present) {
+        if (!a[OVS_FLOW_ATTR_KEY] && !ufid_present) {
                 OVS_NLERR(log,
                           "Flow set message rejected, Key attribute missing.");
-                error = -EINVAL;
+                return -EINVAL;
         }
+
+        error = ovs_nla_init_match_and_action(net, &match, &key, a,
+                                              &acts, log);
         if (error)
                 goto error;
 
-        /* Validate actions. */
-        if (a[OVS_FLOW_ATTR_ACTIONS]) {
-                if (!a[OVS_FLOW_ATTR_KEY]) {
-                        OVS_NLERR(log,
-                                  "Flow key attribute not present in set flow.");
-                        error = -EINVAL;
-                        goto error;
-                }
-
-                acts = get_flow_actions(net, a[OVS_FLOW_ATTR_ACTIONS], &key,
-                                        &mask, log);
-                if (IS_ERR(acts)) {
-                        error = PTR_ERR(acts);
-                        goto error;
-                }
-
+        if (acts) {
                 /* Can allocate before locking if have acts. */
                 reply = ovs_flow_cmd_alloc_info(acts, &sfid, info, false,
                                                 ufid_flags);