* [PATCH 1/2 v2] netfilter: fix the hash random initializing race
@ 2010-08-20 22:48 Changli Gao
2010-09-16 17:56 ` Patrick McHardy
0 siblings, 1 reply; 2+ messages in thread
From: Changli Gao @ 2010-08-20 22:48 UTC (permalink / raw)
To: Patrick McHardy
Cc: Eric Dumazet, Jan Engelhardt, David S. Miller, netfilter-devel,
netdev, Changli Gao
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@gmail.com>
---
v2: fix the coding style for multi-line comment
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 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 */
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 1/2 v2] netfilter: fix the hash random initializing race
2010-08-20 22:48 [PATCH 1/2 v2] netfilter: fix the hash random initializing race Changli Gao
@ 2010-09-16 17:56 ` Patrick McHardy
0 siblings, 0 replies; 2+ messages in thread
From: Patrick McHardy @ 2010-09-16 17:56 UTC (permalink / raw)
To: Changli Gao
Cc: Eric Dumazet, Jan Engelhardt, David S. Miller, netfilter-devel, netdev
On 21.08.2010 00:48, Changli Gao wrote:
> nf_conntrack_alloc() isn't called with nf_conntrack_lock locked, so hash
> random initializing code maybe executed more than once on different CPUs.
>
Applied, thanks. However please remember to use proper subject lines,
we have lots of hashes in netfilter, so without stating that its about
nf_conntrack, its hard to relate this to something without reading the
full changelog.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2010-09-16 17:56 ` Patrick McHardy
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