netfilter: fix the race when initializing nf_ct_expect_hash_rnd

Since nf_ct_expect_dst_hash() may be called without nf_conntrack_lock
locked, nf_ct_expect_hash_rnd should be initialized in the atomic way.

In this patch, we use nf_conntrack_hash_rnd instead of
nf_ct_expect_hash_rnd.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netfilter/nf_conntrack.h

@@ -298,6 +298,8 @@ static inline int nf_ct_is_untracked(const struct nf_conn *ct)
 extern int nf_conntrack_set_hashsize(const char *val, struct kernel_param *kp);
 extern unsigned int nf_conntrack_htable_size;
 extern unsigned int nf_conntrack_max;
+extern unsigned int nf_conntrack_hash_rnd;
+void init_nf_conntrack_hash_rnd(void);
 
 #define NF_CT_STAT_INC(net, count)	\
 	__this_cpu_inc((net)->ct.stat->count)

net/netfilter/nf_conntrack_core.c

@@ -65,7 +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 unsigned int nf_conntrack_hash_rnd __read_mostly;
+unsigned int nf_conntrack_hash_rnd __read_mostly;
 
 static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple, u16 zone)
 {
@@ -596,15 +596,8 @@ static noinline int early_drop(struct net *net, unsigned int hash)
 	return dropped;
 }
 
-static struct nf_conn *
-__nf_conntrack_alloc(struct net *net, u16 zone,
-		     const struct nf_conntrack_tuple *orig,
-		     const struct nf_conntrack_tuple *repl,
-		     gfp_t gfp, u32 hash)
+void init_nf_conntrack_hash_rnd(void)
 {
-	struct nf_conn *ct;
-
-	if (unlikely(!nf_conntrack_hash_rnd)) {
 	unsigned int rand;
 
 	/*
@@ -616,7 +609,18 @@ __nf_conntrack_alloc(struct net *net, u16 zone,
 		get_random_bytes(&rand, sizeof(rand));
 	} while (!rand);
 	cmpxchg(&nf_conntrack_hash_rnd, 0, rand);
+}
 
+static struct nf_conn *
+__nf_conntrack_alloc(struct net *net, u16 zone,
+		     const struct nf_conntrack_tuple *orig,
+		     const struct nf_conntrack_tuple *repl,
+		     gfp_t gfp, u32 hash)
+{
+	struct nf_conn *ct;
+
+	if (unlikely(!nf_conntrack_hash_rnd)) {
+		init_nf_conntrack_hash_rnd();
 		/* recompute the hash as nf_conntrack_hash_rnd is initialized */
 		hash = hash_conntrack_raw(orig, zone);
 	}

net/netfilter/nf_conntrack_expect.c

@@ -32,9 +32,7 @@
 unsigned int nf_ct_expect_hsize __read_mostly;
 EXPORT_SYMBOL_GPL(nf_ct_expect_hsize);
 
-static unsigned int nf_ct_expect_hash_rnd __read_mostly;
 unsigned int nf_ct_expect_max __read_mostly;
-static int nf_ct_expect_hash_rnd_initted __read_mostly;
 
 static struct kmem_cache *nf_ct_expect_cachep __read_mostly;
 
@@ -77,15 +75,13 @@ static unsigned int nf_ct_expect_dst_hash(const struct nf_conntrack_tuple *tuple
 {
 	unsigned int hash;
 
-	if (unlikely(!nf_ct_expect_hash_rnd_initted)) {
-		get_random_bytes(&nf_ct_expect_hash_rnd,
-				 sizeof(nf_ct_expect_hash_rnd));
-		nf_ct_expect_hash_rnd_initted = 1;
+	if (unlikely(!nf_conntrack_hash_rnd)) {
+		init_nf_conntrack_hash_rnd();
 	}
 
 	hash = jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all),
 		      (((tuple->dst.protonum ^ tuple->src.l3num) << 16) |
-		       (__force __u16)tuple->dst.u.all) ^ nf_ct_expect_hash_rnd);
+		       (__force __u16)tuple->dst.u.all) ^ nf_conntrack_hash_rnd);
 	return ((u64)hash * nf_ct_expect_hsize) >> 32;
 }