[NET]: inet_ehash_secret should be __read_mostly and set only once
There is a very tiny probability that build_ehash_secret() is called
at the same time by different CPUS.
Also, using __read_mostly is a must for inet_ehash_secret
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index b7b7278..45ced52 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -218,13 +218,23 @@
return err;
}
-u32 inet_ehash_secret;
+u32 inet_ehash_secret __read_mostly;
EXPORT_SYMBOL(inet_ehash_secret);
+/*
+ * inet_ehash_secret must be set exactly once
+ * Instead of using a dedicated spinlock, we (ab)use inetsw_lock
+ */
void build_ehash_secret(void)
{
- while (!inet_ehash_secret)
- get_random_bytes(&inet_ehash_secret, 4);
+ u32 rnd;
+ do {
+ get_random_bytes(&rnd, sizeof(rnd));
+ } while (rnd == 0);
+ spin_lock_bh(&inetsw_lock);
+ if (!inet_ehash_secret)
+ inet_ehash_secret = rnd;
+ spin_unlock_bh(&inetsw_lock);
}
EXPORT_SYMBOL(build_ehash_secret);