* [PATCH] netfilter: conntrack: fix calculation of next bucket number in early_drop
@ 2018-10-25 3:48 Vasily Khoruzhick
2018-10-25 4:52 ` Dmitry Safonov
0 siblings, 1 reply; 3+ messages in thread
From: Vasily Khoruzhick @ 2018-10-25 3:48 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>
---
net/netfilter/nf_conntrack_core.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index ca1168d67fac..a04af246b184 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;
for (i = 0; i < NF_CT_EVICTION_RANGE; i++) {
struct hlist_nulls_head *ct_hash;
- unsigned int hash, hsize, drops;
+ unsigned int bucket, 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] 3+ messages in thread
* Re: [PATCH] netfilter: conntrack: fix calculation of next bucket number in early_drop
2018-10-25 3:48 [PATCH] netfilter: conntrack: fix calculation of next bucket number in early_drop Vasily Khoruzhick
@ 2018-10-25 4:52 ` Dmitry Safonov
2018-10-25 6:37 ` Vasiliy Khoruzhick
0 siblings, 1 reply; 3+ messages in thread
From: Dmitry Safonov @ 2018-10-25 4:52 UTC (permalink / raw)
To: Vasily Khoruzhick, Pablo Neira Ayuso, Jozsef Kadlecsik,
Florian Westphal, David S. Miller, netfilter-devel, coreteam,
netdev, linux-kernel
Cc: stable
On 10/25/18 4:48 AM, 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.
>
> 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>
Nice work!
Reviewed-by: Dmitry Safonov <dima@arista.com>
> ---
> net/netfilter/nf_conntrack_core.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index ca1168d67fac..a04af246b184 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;
>
> for (i = 0; i < NF_CT_EVICTION_RANGE; i++) {
> struct hlist_nulls_head *ct_hash;
> - unsigned int hash, hsize, drops;
> + unsigned int bucket, 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) {
>
--
Dima
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] netfilter: conntrack: fix calculation of next bucket number in early_drop
2018-10-25 4:52 ` Dmitry Safonov
@ 2018-10-25 6:37 ` Vasiliy Khoruzhick
0 siblings, 0 replies; 3+ messages in thread
From: Vasiliy Khoruzhick @ 2018-10-25 6:37 UTC (permalink / raw)
To: Dmitry Safonov
Cc: Pablo Neira Ayuso, Jozsef Kadlecsik, Florian Westphal,
David S. Miller, netfilter-devel, coreteam, netdev, linux-kernel,
stable
On Wed, Oct 24, 2018 at 9:52 PM, Dmitry Safonov <dima@arista.com> wrote:
> On 10/25/18 4:48 AM, 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.
>>
>> 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>
>
>
> Nice work!
>
> Reviewed-by: Dmitry Safonov <dima@arista.com>
Oops, found a bug in it - 'bucket' should be moved outside of the
loop. I'll send v2 tomorrow morning.
>
>> ---
>> net/netfilter/nf_conntrack_core.c | 11 +++++++----
>> 1 file changed, 7 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/netfilter/nf_conntrack_core.c
>> b/net/netfilter/nf_conntrack_core.c
>> index ca1168d67fac..a04af246b184 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;
>> for (i = 0; i < NF_CT_EVICTION_RANGE; i++) {
>> struct hlist_nulls_head *ct_hash;
>> - unsigned int hash, hsize, drops;
>> + unsigned int bucket, 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) {
>>
>
> --
> Dima
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-10-25 3:48 [PATCH] netfilter: conntrack: fix calculation of next bucket number in early_drop Vasily Khoruzhick
2018-10-25 4:52 ` Dmitry Safonov
2018-10-25 6:37 ` Vasiliy Khoruzhick
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