inet fragments: fix race between inet_frag_find and inet_frag_secret_rebuild

The problem is that while we work w/o the inet_frags.lock even
read-locked the secret rebuild timer may occur (on another CPU, since
BHs are still disabled in the inet_frag_find) and change the rnd seed
for ipv4/6 fragments.

It was caused by my patch fd9e63544cac30a34c951f0ec958038f0529e244
([INET]: Omit double hash calculations in xxx_frag_intern) late 
in the 2.6.24 kernel, so this should probably be queued to -stable.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index cd6ce6ac6358..37221f659159 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -229,6 +229,8 @@ static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
 
         arg.iph = iph;
         arg.user = user;
+
+        read_lock(&ip4_frags.lock);
         hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
 
         q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);