From b23909695c33f53df5f1d16696b1aa5b874c1904 Mon Sep 17 00:00:00 2001 From: Changli Gao Date: Thu, 16 Sep 2010 19:55:03 +0200 Subject: [PATCH] netfilter: nf_conntrack: fix the hash random initializing race 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 Signed-off-by: Patrick McHardy --- net/netfilter/nf_conntrack_core.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index df3eedb142ff..4c0ad9b4dba0 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 */ -- GitLab