[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>

3 files changed, 15 insertions, 9 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
diff --git a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
index a2353edf4ebc..4b7be4bb4d03 100644
--- a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
@@ -154,8 +154,8 @@ ipv6_prepare(struct sk_buff **pskb, unsigned int hooknum, unsigned int *dataoff,
          */
         if ((protoff < 0) || (protoff > (*pskb)->len)) {
                 DEBUGP("ip6_conntrack_core: can't find proto in pkt\n");
-                NF_CT_STAT_INC(error);
-                NF_CT_STAT_INC(invalid);
+                NF_CT_STAT_INC_ATOMIC(error);
+                NF_CT_STAT_INC_ATOMIC(invalid);
                 return -NF_ACCEPT;
         }
 
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 3deeb900263b..d59640e2377b 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -563,7 +563,7 @@ static int early_drop(struct list_head *chain)
         if (del_timer(&ct->timeout)) {
                 death_by_timeout((unsigned long)ct);
                 dropped = 1;
-                NF_CT_STAT_INC(early_drop);
+                NF_CT_STAT_INC_ATOMIC(early_drop);
         }
         nf_ct_put(ct);
         return dropped;
@@ -821,7 +821,7 @@ nf_conntrack_in(int pf, unsigned int hooknum, struct sk_buff **pskb)
 
         /* Previously seen (loopback or untracked)?  Ignore. */
         if ((*pskb)->nfct) {
-                NF_CT_STAT_INC(ignore);
+                NF_CT_STAT_INC_ATOMIC(ignore);
                 return NF_ACCEPT;
         }
 
@@ -840,8 +840,8 @@ nf_conntrack_in(int pf, unsigned int hooknum, struct sk_buff **pskb)
          * core what to do with the packet. */
         if (l4proto->error != NULL &&
             (ret = l4proto->error(*pskb, dataoff, &ctinfo, pf, hooknum)) <= 0) {
-                NF_CT_STAT_INC(error);
-                NF_CT_STAT_INC(invalid);
+                NF_CT_STAT_INC_ATOMIC(error);
+                NF_CT_STAT_INC_ATOMIC(invalid);
                 return -ret;
         }
 
@@ -849,13 +849,13 @@ nf_conntrack_in(int pf, unsigned int hooknum, struct sk_buff **pskb)
                                &set_reply, &ctinfo);
         if (!ct) {
                 /* Not valid part of a connection */
-                NF_CT_STAT_INC(invalid);
+                NF_CT_STAT_INC_ATOMIC(invalid);
                 return NF_ACCEPT;
         }
 
         if (IS_ERR(ct)) {
                 /* Too stressed to deal. */
-                NF_CT_STAT_INC(drop);
+                NF_CT_STAT_INC_ATOMIC(drop);
                 return NF_DROP;
         }
 
@@ -868,7 +868,7 @@ nf_conntrack_in(int pf, unsigned int hooknum, struct sk_buff **pskb)
                 DEBUGP("nf_conntrack_in: Can't track with proto module\n");
                 nf_conntrack_put((*pskb)->nfct);
                 (*pskb)->nfct = NULL;
-                NF_CT_STAT_INC(invalid);
+                NF_CT_STAT_INC_ATOMIC(invalid);
                 return -ret;
         }