netfilter: nf_tables: add clone interface to expression operations

With the conversion of the counter expressions to make it percpu, we
need to clone the percpu memory area, otherwise we crash when using
counters from flow tables.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_tables.h

@@ -618,6 +618,8 @@ struct nft_expr_ops {
 	void				(*eval)(const struct nft_expr *expr,
 						struct nft_regs *regs,
 						const struct nft_pktinfo *pkt);
+	int				(*clone)(struct nft_expr *dst,
+						 const struct nft_expr *src);
 	unsigned int			size;
 
 	int				(*init)(const struct nft_ctx *ctx,
@@ -660,10 +662,20 @@ void nft_expr_destroy(const struct nft_ctx *ctx, struct nft_expr *expr);
 int nft_expr_dump(struct sk_buff *skb, unsigned int attr,
 		  const struct nft_expr *expr);
 
-static inline void nft_expr_clone(struct nft_expr *dst, struct nft_expr *src)
+static inline int nft_expr_clone(struct nft_expr *dst, struct nft_expr *src)
 {
+	int err;
+
 	__module_get(src->ops->type->owner);
-	memcpy(dst, src, src->ops->size);
+	if (src->ops->clone) {
+		dst->ops = src->ops;
+		err = src->ops->clone(dst, src);
+		if (err < 0)
+			return err;
+	} else {
+		memcpy(dst, src, src->ops->size);
+	}
+	return 0;
 }
 
 /**

net/netfilter/nft_counter.c

@@ -47,27 +47,34 @@ static void nft_counter_eval(const struct nft_expr *expr,
 	local_bh_enable();
 }
 
-static int nft_counter_dump(struct sk_buff *skb, const struct nft_expr *expr)
+static void nft_counter_fetch(const struct nft_counter_percpu __percpu *counter,
+			      struct nft_counter *total)
 {
-	struct nft_counter_percpu_priv *priv = nft_expr_priv(expr);
-	struct nft_counter_percpu *cpu_stats;
-	struct nft_counter total;
+	const struct nft_counter_percpu *cpu_stats;
 	u64 bytes, packets;
 	unsigned int seq;
 	int cpu;
 
-	memset(&total, 0, sizeof(total));
+	memset(total, 0, sizeof(*total));
 	for_each_possible_cpu(cpu) {
-		cpu_stats = per_cpu_ptr(priv->counter, cpu);
+		cpu_stats = per_cpu_ptr(counter, cpu);
 		do {
 			seq	= u64_stats_fetch_begin_irq(&cpu_stats->syncp);
 			bytes	= cpu_stats->counter.bytes;
 			packets	= cpu_stats->counter.packets;
 		} while (u64_stats_fetch_retry_irq(&cpu_stats->syncp, seq));
 
-		total.packets += packets;
-		total.bytes += bytes;
+		total->packets += packets;
+		total->bytes += bytes;
 	}
+}
+
+static int nft_counter_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	struct nft_counter_percpu_priv *priv = nft_expr_priv(expr);
+	struct nft_counter total;
+
+	nft_counter_fetch(priv->counter, &total);
 
 	if (nla_put_be64(skb, NFTA_COUNTER_BYTES, cpu_to_be64(total.bytes)) ||
 	    nla_put_be64(skb, NFTA_COUNTER_PACKETS, cpu_to_be64(total.packets)))
@@ -118,6 +125,31 @@ static void nft_counter_destroy(const struct nft_ctx *ctx,
 	free_percpu(priv->counter);
 }
 
+static int nft_counter_clone(struct nft_expr *dst, const struct nft_expr *src)
+{
+	struct nft_counter_percpu_priv *priv = nft_expr_priv(src);
+	struct nft_counter_percpu_priv *priv_clone = nft_expr_priv(dst);
+	struct nft_counter_percpu __percpu *cpu_stats;
+	struct nft_counter_percpu *this_cpu;
+	struct nft_counter total;
+
+	nft_counter_fetch(priv->counter, &total);
+
+	cpu_stats = __netdev_alloc_pcpu_stats(struct nft_counter_percpu,
+					      GFP_ATOMIC);
+	if (cpu_stats == NULL)
+		return ENOMEM;
+
+	preempt_disable();
+	this_cpu = this_cpu_ptr(cpu_stats);
+	this_cpu->counter.packets = total.packets;
+	this_cpu->counter.bytes = total.bytes;
+	preempt_enable();
+
+	priv_clone->counter = cpu_stats;
+	return 0;
+}
+
 static struct nft_expr_type nft_counter_type;
 static const struct nft_expr_ops nft_counter_ops = {
 	.type		= &nft_counter_type,
@@ -126,6 +158,7 @@ static const struct nft_expr_ops nft_counter_ops = {
 	.init		= nft_counter_init,
 	.destroy	= nft_counter_destroy,
 	.dump		= nft_counter_dump,
+	.clone		= nft_counter_clone,
 };
 
 static struct nft_expr_type nft_counter_type __read_mostly = {

net/netfilter/nft_dynset.c

@@ -50,8 +50,9 @@ static void *nft_dynset_new(struct nft_set *set, const struct nft_expr *expr,
 	}
 
 	ext = nft_set_elem_ext(set, elem);
-	if (priv->expr != NULL)
-		nft_expr_clone(nft_set_ext_expr(ext), priv->expr);
+	if (priv->expr != NULL &&
+	    nft_expr_clone(nft_set_ext_expr(ext), priv->expr) < 0)
+		return NULL;
 
 	return elem;
 }