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| author | Changli Gao <xiaosuo@gmail.com> | 2010-09-16 19:55:03 +0200 |
|---|---|---|
| committer | Patrick McHardy <kaber@trash.net> | 2010-09-16 19:55:03 +0200 |
| commit | b23909695c33f53df5f1d16696b1aa5b874c1904 (patch) | |
| tree | 94293e4d5c9a71751dacf5b2a34735428010ff2e /net/netfilter | |
| parent | ed0b6d7581b54455062f09ccac123814e70cd02f (diff) | |
| download | linux-b23909695c33f53df5f1d16696b1aa5b874c1904.tar.gz linux-b23909695c33f53df5f1d16696b1aa5b874c1904.tar.bz2 linux-b23909695c33f53df5f1d16696b1aa5b874c1904.zip | |
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 <xiaosuo@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Diffstat (limited to 'net/netfilter')
| -rw-r--r-- | 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 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 */ |