提交 caa41527 编写于 作者: E Eric Dumazet 提交者: David S. Miller

ipv4: fix a race in update_or_create_fnhe()

nh_exceptions is effectively used under rcu, but lacks proper
barriers. Between kzalloc() and setting of nh->nh_exceptions(),
we need a proper memory barrier.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Fixes: 4895c771 ("ipv4: Add FIB nexthop exceptions.")
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
上级 29abe2fd
......@@ -87,7 +87,7 @@ struct fib_nh {
int nh_saddr_genid;
struct rtable __rcu * __percpu *nh_pcpu_rth_output;
struct rtable __rcu *nh_rth_input;
struct fnhe_hash_bucket *nh_exceptions;
struct fnhe_hash_bucket __rcu *nh_exceptions;
};
/*
......
......@@ -157,9 +157,12 @@ static void rt_fibinfo_free(struct rtable __rcu **rtp)
static void free_nh_exceptions(struct fib_nh *nh)
{
struct fnhe_hash_bucket *hash = nh->nh_exceptions;
struct fnhe_hash_bucket *hash;
int i;
hash = rcu_dereference_protected(nh->nh_exceptions, 1);
if (!hash)
return;
for (i = 0; i < FNHE_HASH_SIZE; i++) {
struct fib_nh_exception *fnhe;
......@@ -205,8 +208,7 @@ static void free_fib_info_rcu(struct rcu_head *head)
change_nexthops(fi) {
if (nexthop_nh->nh_dev)
dev_put(nexthop_nh->nh_dev);
if (nexthop_nh->nh_exceptions)
free_nh_exceptions(nexthop_nh);
free_nh_exceptions(nexthop_nh);
rt_fibinfo_free_cpus(nexthop_nh->nh_pcpu_rth_output);
rt_fibinfo_free(&nexthop_nh->nh_rth_input);
} endfor_nexthops(fi);
......
......@@ -628,12 +628,12 @@ static void update_or_create_fnhe(struct fib_nh *nh, __be32 daddr, __be32 gw,
spin_lock_bh(&fnhe_lock);
hash = nh->nh_exceptions;
hash = rcu_dereference(nh->nh_exceptions);
if (!hash) {
hash = kzalloc(FNHE_HASH_SIZE * sizeof(*hash), GFP_ATOMIC);
if (!hash)
goto out_unlock;
nh->nh_exceptions = hash;
rcu_assign_pointer(nh->nh_exceptions, hash);
}
hash += hval;
......@@ -1242,7 +1242,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst)
static struct fib_nh_exception *find_exception(struct fib_nh *nh, __be32 daddr)
{
struct fnhe_hash_bucket *hash = nh->nh_exceptions;
struct fnhe_hash_bucket *hash = rcu_dereference(nh->nh_exceptions);
struct fib_nh_exception *fnhe;
u32 hval;
......
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