netfilter: nfnetlink_acct: avoid using NFACCT_F_OVERQUOTA with bit helper functions

Bit helper functions were used for manipulation with NFACCT_F_OVERQUOTA,
but they are accepting pit position, but not a bit mask. As a result
not a third bit for NFACCT_F_OVERQUOTA was set, but forth. Such
behaviour was dangarous and could lead to unexpected overquota report
result.
Signed-off-by: Alexey Perevalov <a.perevalov@samsung.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink_acct.c

@@ -41,6 +41,7 @@ struct nf_acct {
 };
 
 #define NFACCT_F_QUOTA (NFACCT_F_QUOTA_PKTS | NFACCT_F_QUOTA_BYTES)
+#define NFACCT_OVERQUOTA_BIT	2	/* NFACCT_F_OVERQUOTA */
 
 static int
 nfnl_acct_new(struct sock *nfnl, struct sk_buff *skb,
@@ -77,7 +78,8 @@ nfnl_acct_new(struct sock *nfnl, struct sk_buff *skb,
 			smp_mb__before_atomic();
 			/* reset overquota flag if quota is enabled. */
 			if ((matching->flags & NFACCT_F_QUOTA))
-				clear_bit(NFACCT_F_OVERQUOTA, &matching->flags);
+				clear_bit(NFACCT_OVERQUOTA_BIT,
+					  &matching->flags);
 			return 0;
 		}
 		return -EBUSY;
@@ -150,7 +152,7 @@ nfnl_acct_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
 		bytes = atomic64_xchg(&acct->bytes, 0);
 		smp_mb__before_atomic();
 		if (acct->flags & NFACCT_F_QUOTA)
-			clear_bit(NFACCT_F_OVERQUOTA, &acct->flags);
+			clear_bit(NFACCT_OVERQUOTA_BIT, &acct->flags);
 	} else {
 		pkts = atomic64_read(&acct->pkts);
 		bytes = atomic64_read(&acct->bytes);
@@ -414,7 +416,7 @@ int nfnl_acct_overquota(const struct sk_buff *skb, struct nf_acct *nfacct)
 	ret = now > *quota;
 
 	if (now >= *quota &&
-	    !test_and_set_bit(NFACCT_F_OVERQUOTA, &nfacct->flags)) {
+	    !test_and_set_bit(NFACCT_OVERQUOTA_BIT, &nfacct->flags)) {
 		nfnl_overquota_report(nfacct);
 	}