* [PATCH v2] netfilter: conntrack: fix calculation of next bucket number in early_drop
@ 2018-10-25 19:15 Vasily Khoruzhick
2018-11-03 13:16 ` Pablo Neira Ayuso
0 siblings, 1 reply; 2+ messages in thread
From: Vasily Khoruzhick @ 2018-10-25 19:15 UTC (permalink / raw)
To: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
David S. Miller, netfilter-devel, coreteam, netdev, linux-kernel,
Dmitry Safonov
Cc: Vasily Khoruzhick, stable
If there's no entry to drop in bucket that corresponds to the hash,
early_drop() should look for it in other buckets. But since it increments
hash instead of bucket number, it actually looks in the same bucket 8
times: hsize is 16k by default (14 bits) and hash is 32-bit value, so
reciprocal_scale(hash, hsize) returns the same value for hash..hash+7 in
most cases.
Fix it by increasing bucket number instead of hash and rename _hash
to bucket to avoid future confusion.
Fixes: 3e86638e9a0b ("netfilter: conntrack: consider ct netns in early_drop logic")
Cc: <stable@vger.kernel.org> # v4.7+
Signed-off-by: Vasily Khoruzhick <vasilykh@arista.com>
---
v2: move 'bucket' outside of the loop
net/netfilter/nf_conntrack_core.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index ca1168d67fac..e92e749aff53 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1073,19 +1073,22 @@ static unsigned int early_drop_list(struct net *net,
return drops;
}
-static noinline int early_drop(struct net *net, unsigned int _hash)
+static noinline int early_drop(struct net *net, unsigned int hash)
{
- unsigned int i;
+ unsigned int i, bucket;
for (i = 0; i < NF_CT_EVICTION_RANGE; i++) {
struct hlist_nulls_head *ct_hash;
- unsigned int hash, hsize, drops;
+ unsigned int hsize, drops;
rcu_read_lock();
nf_conntrack_get_ht(&ct_hash, &hsize);
- hash = reciprocal_scale(_hash++, hsize);
+ if (!i)
+ bucket = reciprocal_scale(hash, hsize);
+ else
+ bucket = (bucket + 1) % hsize;
- drops = early_drop_list(net, &ct_hash[hash]);
+ drops = early_drop_list(net, &ct_hash[bucket]);
rcu_read_unlock();
if (drops) {
--
2.19.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] netfilter: conntrack: fix calculation of next bucket number in early_drop
2018-10-25 19:15 [PATCH v2] netfilter: conntrack: fix calculation of next bucket number in early_drop Vasily Khoruzhick
@ 2018-11-03 13:16 ` Pablo Neira Ayuso
0 siblings, 0 replies; 2+ messages in thread
From: Pablo Neira Ayuso @ 2018-11-03 13:16 UTC (permalink / raw)
To: Vasily Khoruzhick
Cc: Jozsef Kadlecsik, Florian Westphal, David S. Miller,
netfilter-devel, coreteam, netdev, linux-kernel, Dmitry Safonov,
stable
On Thu, Oct 25, 2018 at 12:15:43PM -0700, Vasily Khoruzhick wrote:
> If there's no entry to drop in bucket that corresponds to the hash,
> early_drop() should look for it in other buckets. But since it increments
> hash instead of bucket number, it actually looks in the same bucket 8
> times: hsize is 16k by default (14 bits) and hash is 32-bit value, so
> reciprocal_scale(hash, hsize) returns the same value for hash..hash+7 in
> most cases.
>
> Fix it by increasing bucket number instead of hash and rename _hash
> to bucket to avoid future confusion.
Applied, thanks.
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