From: Changli Gao <xiaosuo@xxxxxxxxx>
nf_conntrack_alloc() isn't called with nf_conntrack_lock locked, so hash
random initializing code maybe executed more than once on different
CPUs.
Signed-off-by: Changli Gao <xiaosuo@xxxxxxxxx>
Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
---
net/netfilter/nf_conntrack_core.c | 19 +++++++++++++------
1 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index df3eedb..4c0ad9b 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -65,8 +65,7 @@ EXPORT_SYMBOL_GPL(nf_conntrack_max);
DEFINE_PER_CPU(struct nf_conn, nf_conntrack_untracked);
EXPORT_PER_CPU_SYMBOL(nf_conntrack_untracked);
-static int nf_conntrack_hash_rnd_initted;
-static unsigned int nf_conntrack_hash_rnd;
+static unsigned int nf_conntrack_hash_rnd __read_mostly;
static u_int32_t __hash_conntrack(const struct nf_conntrack_tuple *tuple,
u16 zone, unsigned int size, unsigned int rnd)
@@ -574,10 +573,18 @@ struct nf_conn *nf_conntrack_alloc(struct net *net, u16 zone,
{
struct nf_conn *ct;
- if (unlikely(!nf_conntrack_hash_rnd_initted)) {
- get_random_bytes(&nf_conntrack_hash_rnd,
- sizeof(nf_conntrack_hash_rnd));
- nf_conntrack_hash_rnd_initted = 1;
+ if (unlikely(!nf_conntrack_hash_rnd)) {
+ unsigned int rand;
+
+ /*
+ * Why not initialize nf_conntrack_rnd in a "init()" function ?
+ * Because there isn't enough entropy when system initializing,
+ * and we initialize it as late as possible.
+ */
+ do {
+ get_random_bytes(&rand, sizeof(rand));
+ } while (!rand);
+ cmpxchg(&nf_conntrack_hash_rnd, 0, rand);
}
/* We don't want any race condition at early drop stage */
--
1.7.1
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