Byte-rate limits using long time units (e.g. bytes/week) can overflow
priv->nsecs * skb->len in the packet-path cost calculation, silently
defeating the configured rate limit.

Reject such configurations at rule-add time instead, using the GRO
maximum packet size as a conservative bound on skb length for the
multiplication check.

Fixes: d2168e849ebf ("netfilter: nft_limit: add per-byte limiting")
Signed-off-by: SaifAllah benMassaoud <saifmassaoudi18@gmail.com>

diff --git a/net/netfilter/nft_limit.c b/net/netfilter/nft_limit.c
index d92455fc8665..07dc5c55b0a0 100644
--- a/net/netfilter/nft_limit.c
+++ b/net/netfilter/nft_limit.c
@@ -13,7 +13,7 @@
 #include <linux/netfilter.h>
 #include <linux/netfilter/nf_tables.h>
 #include <net/netfilter/nf_tables.h>
-#include <net/gro.h>
+#include <linux/netdevice.h>
 
 struct nft_limit {
 	spinlock_t	lock;
@@ -59,7 +59,7 @@ static inline bool nft_limit_eval(struct nft_limit_priv *priv, u64 cost)
 static int nft_limit_init(struct nft_limit_priv *priv,
 			  const struct nlattr * const tb[], bool pkts)
 {
-	u64 unit, tmp, tokens, rate_with_burst;
+	u64 unit, tokens, rate_with_burst;
 	bool invert = false;
 
 	if (tb[NFTA_LIMIT_RATE] == NULL ||
@@ -74,8 +74,7 @@ static int nft_limit_init(struct nft_limit_priv *priv,
 	if (check_mul_overflow(unit, NSEC_PER_SEC, &priv->nsecs))
 		return -EOVERFLOW;
 
-	if (!pkts &&
-	    check_mul_overflow(priv->nsecs, GRO_MAX_SIZE, &tmp))
+	if (!pkts && priv->nsecs > U64_MAX / GRO_MAX_SIZE)
 		return -EOVERFLOW;
 
 	if (tb[NFTA_LIMIT_BURST])