netfilter: nft_quota: reset quota after dump

Dumping of netlink attributes may fail due to insufficient room in the
skbuff, so let's reset consumed quota if we succeed to put netlink
attributes into the skbuff.

Fixes: 43da04a593d8 ("netfilter: nf_tables: atomic dump and reset for stateful objects")
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_quota.c

@@ -110,30 +110,32 @@ static int nft_quota_obj_init(const struct nlattr * const tb[],
 static int nft_quota_do_dump(struct sk_buff *skb, struct nft_quota *priv,
 			     bool reset)
 {
+	u64 consumed, consumed_cap;
 	u32 flags = priv->flags;
-	u64 consumed;
-
-	if (reset) {
-		consumed = atomic64_xchg(&priv->consumed, 0);
-		if (test_and_clear_bit(NFT_QUOTA_DEPLETED_BIT, &priv->flags))
-			flags |= NFT_QUOTA_F_DEPLETED;
-	} else {
-		consumed = atomic64_read(&priv->consumed);
-	}
 
 	/* Since we inconditionally increment consumed quota for each packet
 	 * that we see, don't go over the quota boundary in what we send to
 	 * userspace.
 	 */
-	if (consumed > priv->quota)
-		consumed = priv->quota;
+	consumed = atomic64_read(&priv->consumed);
+	if (consumed >= priv->quota) {
+		consumed_cap = priv->quota;
+		flags |= NFT_QUOTA_F_DEPLETED;
+	} else {
+		consumed_cap = consumed;
+	}
 
 	if (nla_put_be64(skb, NFTA_QUOTA_BYTES, cpu_to_be64(priv->quota),
 			 NFTA_QUOTA_PAD) ||
-	    nla_put_be64(skb, NFTA_QUOTA_CONSUMED, cpu_to_be64(consumed),
+	    nla_put_be64(skb, NFTA_QUOTA_CONSUMED, cpu_to_be64(consumed_cap),
 			 NFTA_QUOTA_PAD) ||
 	    nla_put_be32(skb, NFTA_QUOTA_FLAGS, htonl(flags)))
 		goto nla_put_failure;
+
+	if (reset) {
+		atomic64_sub(consumed, &priv->consumed);
+		clear_bit(NFT_QUOTA_DEPLETED_BIT, &priv->flags);
+	}
 	return 0;
 
 nla_put_failure: