[NETFILTER]: ip_conntrack: fix invalid conntrack statistics RCU assumption

CONNTRACK_STAT_INC assumes rcu_read_lock in nf_hook_slow disables
preemption as well, making it legal to use __get_cpu_var without
disabling preemption manually. The assumption is not correct anymore
with preemptable RCU, additionally we need to protect against softirqs
when not holding ip_conntrack_lock.

Add CONNTRACK_STAT_INC_ATOMIC macro, which disables local softirqs,
and use where necessary.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/netfilter_ipv4/ip_conntrack.h b/include/linux/netfilter_ipv4/ip_conntrack.h
index 33581c13d947..da9274e6bf12 100644
--- a/include/linux/netfilter_ipv4/ip_conntrack.h
+++ b/include/linux/netfilter_ipv4/ip_conntrack.h
@@ -301,6 +301,12 @@ extern unsigned int ip_conntrack_htable_size;
 extern int ip_conntrack_checksum;
  
 #define CONNTRACK_STAT_INC(count) (__get_cpu_var(ip_conntrack_stat).count++)
+#define CONNTRACK_STAT_INC_ATOMIC(count)                \
+do {                                                    \
+        local_bh_disable();                             \
+        __get_cpu_var(ip_conntrack_stat).count++;       \
+        local_bh_enable();                              \
+} while (0)
 
 #ifdef CONFIG_IP_NF_CONNTRACK_EVENTS
 #include <linux/notifier.h>