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netfilter: nft_limit: reject configurations that cause integer overflow

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Reject bogus configs where internal token counter wraps around.
This only occurs with very very large requests, such as 17gbyte/s.

Its better to reject this rather than having incorrect ratelimit.

Fixes: d2168e849e ("netfilter: nft_limit: add per-byte limiting")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2024-01-19 13:11:32 +01:00 committed by Pablo Neira Ayuso
parent 01acb2e866
commit c9d9eb9c53
1 changed files with 16 additions and 7 deletions
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23
net/netfilter/nft_limit.c
View file

@ -58,17 +58,19 @@ 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, tokens, rate_with_burst;
bool invert = false;
u64 unit, tokens;
if (tb[NFTA_LIMIT_RATE] == NULL ||
tb[NFTA_LIMIT_UNIT] == NULL)
return -EINVAL;
priv->rate = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_RATE]));
if (priv->rate == 0)
return -EINVAL;
unit = be64_to_cpu(nla_get_be64(tb[NFTA_LIMIT_UNIT]));
priv->nsecs = unit * NSEC_PER_SEC;
if (priv->rate == 0 || priv->nsecs < unit)
if (check_mul_overflow(unit, NSEC_PER_SEC, &priv->nsecs))
return -EOVERFLOW;
if (tb[NFTA_LIMIT_BURST])
@ -77,18 +79,25 @@ static int nft_limit_init(struct nft_limit_priv *priv,
if (pkts && priv->burst == 0)
priv->burst = NFT_LIMIT_PKT_BURST_DEFAULT;
if (priv->rate + priv->burst < priv->rate)
if (check_add_overflow(priv->rate, priv->burst, &rate_with_burst))
return -EOVERFLOW;
if (pkts) {
tokens = div64_u64(priv->nsecs, priv->rate) * priv->burst;
u64 tmp = div64_u64(priv->nsecs, priv->rate);
if (check_mul_overflow(tmp, priv->burst, &tokens))
return -EOVERFLOW;
} else {
u64 tmp;
/* The token bucket size limits the number of tokens can be
* accumulated. tokens_max specifies the bucket size.
* tokens_max = unit * (rate + burst) / rate.
*/
tokens = div64_u64(priv->nsecs * (priv->rate + priv->burst),
priv->rate);
if (check_mul_overflow(priv->nsecs, rate_with_burst, &tmp))
return -EOVERFLOW;
tokens = div64_u64(tmp, priv->rate);
}
if (tb[NFTA_LIMIT_FLAGS]) {