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) {
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);elsebucket = (bucket + 1) % hsize;
drops = early_drop_list(net, &ct_hash[hash]);
drops = early_drop_list(net, &ct_hash[bucket]);if (drops) {
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);elsebucket = (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
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Vasily Khoruzhick