On 06/27/2017 12:03 AM, Tonghao Zhang wrote:
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....@gmail.com>
---
  datapath/datapath.c | 11 ++++++++---
  1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/datapath/datapath.c b/datapath/datapath.c
index c85029c..da8cd68 100644
--- a/datapath/datapath.c
+++ b/datapath/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;
  }


It looks fine to me but let's copy the maintainer Pravin

- Greg

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