[PATCH] netlink: don't copy over empty attribute data

[Sasha Levin]

netlink uses empty data to seperate different levels. However, we still
try to copy that data from a NULL ptr using memcpy, which is an undefined
behaviour.

Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
 lib/nlattr.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/nlattr.c b/lib/nlattr.c
index 9c3e85f..6512b43 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -430,7 +430,8 @@ void __nla_put(struct sk_buff *skb, int attrtype, int attrlen,
 	struct nlattr *nla;
 
 	nla = __nla_reserve(skb, attrtype, attrlen);
-	memcpy(nla_data(nla), data, attrlen);
+	if (data)
+		memcpy(nla_data(nla), data, attrlen);
 }
 EXPORT_SYMBOL(__nla_put);
 
-- 
1.7.10.4

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