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: Eric Dumazet <edumazet@google.com>
Fixes: 4895c771c7f00 ("ipv4: Add FIB nexthop exceptions.")
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index eaa4b00..44b0cbd 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -628,12 +628,12 @@
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 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;