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Date:   Wed, 31 Aug 2016 10:56:19 +0800
Subject: [PATCH net] rps: flow_dissector: Fix uninitialized flow_keys used in __skb_get_hash possibly

From: Gao Feng <>

The original codes depend on that the function parameters are evaluated from
left to right. But the parameter's evaluation order is not defined in C
standard actually.

When flow_keys_have_l4(&keys) is invoked before ___skb_get_hash(skb, &keys,
hashrnd) with some compilers or environment, the keys passed to
flow_keys_have_l4 is not initialized.

Signed-off-by: Gao Feng <>
 net/core/flow_dissector.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 61ad43f..52742a0 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -680,11 +680,13 @@ EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric);
 void __skb_get_hash(struct sk_buff *skb)
 	struct flow_keys keys;
+	u32 hash;
-	__skb_set_sw_hash(skb, ___skb_get_hash(skb, &keys, hashrnd),
-			  flow_keys_have_l4(&keys));
+	hash = ___skb_get_hash(skb, &keys, hashrnd);
+	__skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));

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