From be776281aee54626a474ba06f91926b98bdd180d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 27 Mar 2007 13:53:04 -0700 Subject: [PATCH] [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 Signed-off-by: David S. Miller --- net/ipv4/af_inet.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index b7b7278d801c..45ced52c03d4 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -218,13 +218,23 @@ out: 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); -- 2.30.2