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

NF_CT_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 nf_conntrack_lock.

Add NF_CT_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/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index 68ec27490c20..0e690e34c00b 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -257,6 +257,12 @@ extern int nf_conntrack_max;
 
 DECLARE_PER_CPU(struct ip_conntrack_stat, nf_conntrack_stat);
 #define NF_CT_STAT_INC(count) (__get_cpu_var(nf_conntrack_stat).count++)
+#define NF_CT_STAT_INC_ATOMIC(count)                    \
+do {                                                    \
+        local_bh_disable();                             \
+        __get_cpu_var(nf_conntrack_stat).count++;       \
+        local_bh_enable();                              \
+} while (0)
 
 /* no helper, no nat */
 #define NF_CT_F_BASIC   0