netfilter: nf_conntrack: per netns nf_conntrack_cachep
nf_conntrack_cachep is currently shared by all netns instances, but
because of SLAB_DESTROY_BY_RCU special semantics, this is wrong.
If we use a shared slab cache, one object can instantly flight between
one hash table (netns ONE) to another one (netns TWO), and concurrent
reader (doing a lookup in netns ONE, 'finding' an object of netns TWO)
can be fooled without notice, because no RCU grace period has to be
observed between object freeing and its reuse.
We dont have this problem with UDP/TCP slab caches because TCP/UDP
hashtables are global to the machine (and each object has a pointer to
its netns).
If we use per netns conntrack hash tables, we also *must* use per netns
conntrack slab caches, to guarantee an object can not escape from one
namespace to another one.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
[Patrick: added unique slab name allocation]
Cc: stable@kernel.org
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 37e2b88..9de4bd4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -63,8 +63,6 @@
struct nf_conn nf_conntrack_untracked __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_untracked);
-static struct kmem_cache *nf_conntrack_cachep __read_mostly;
-
static int nf_conntrack_hash_rnd_initted;
static unsigned int nf_conntrack_hash_rnd;
@@ -572,7 +570,7 @@
* Do not use kmem_cache_zalloc(), as this cache uses
* SLAB_DESTROY_BY_RCU.
*/
- ct = kmem_cache_alloc(nf_conntrack_cachep, gfp);
+ ct = kmem_cache_alloc(net->ct.nf_conntrack_cachep, gfp);
if (ct == NULL) {
pr_debug("nf_conntrack_alloc: Can't alloc conntrack.\n");
atomic_dec(&net->ct.count);
@@ -611,7 +609,7 @@
nf_ct_ext_destroy(ct);
atomic_dec(&net->ct.count);
nf_ct_ext_free(ct);
- kmem_cache_free(nf_conntrack_cachep, ct);
+ kmem_cache_free(net->ct.nf_conntrack_cachep, ct);
}
EXPORT_SYMBOL_GPL(nf_conntrack_free);
@@ -1119,7 +1117,6 @@
nf_conntrack_helper_fini();
nf_conntrack_proto_fini();
- kmem_cache_destroy(nf_conntrack_cachep);
}
static void nf_conntrack_cleanup_net(struct net *net)
@@ -1137,6 +1134,8 @@
nf_conntrack_ecache_fini(net);
nf_conntrack_acct_fini(net);
nf_conntrack_expect_fini(net);
+ kmem_cache_destroy(net->ct.nf_conntrack_cachep);
+ kfree(net->ct.slabname);
free_percpu(net->ct.stat);
}
@@ -1272,15 +1271,6 @@
NF_CONNTRACK_VERSION, nf_conntrack_htable_size,
nf_conntrack_max);
- nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
- sizeof(struct nf_conn),
- 0, SLAB_DESTROY_BY_RCU, NULL);
- if (!nf_conntrack_cachep) {
- printk(KERN_ERR "Unable to create nf_conn slab cache\n");
- ret = -ENOMEM;
- goto err_cache;
- }
-
ret = nf_conntrack_proto_init();
if (ret < 0)
goto err_proto;
@@ -1302,8 +1292,6 @@
err_helper:
nf_conntrack_proto_fini();
err_proto:
- kmem_cache_destroy(nf_conntrack_cachep);
-err_cache:
return ret;
}
@@ -1325,6 +1313,21 @@
ret = -ENOMEM;
goto err_stat;
}
+
+ net->ct.slabname = kasprintf(GFP_KERNEL, "nf_conntrack_%p", net);
+ if (!net->ct.slabname) {
+ ret = -ENOMEM;
+ goto err_slabname;
+ }
+
+ net->ct.nf_conntrack_cachep = kmem_cache_create(net->ct.slabname,
+ sizeof(struct nf_conn), 0,
+ SLAB_DESTROY_BY_RCU, NULL);
+ if (!net->ct.nf_conntrack_cachep) {
+ printk(KERN_ERR "Unable to create nf_conn slab cache\n");
+ ret = -ENOMEM;
+ goto err_cache;
+ }
net->ct.hash = nf_ct_alloc_hashtable(&nf_conntrack_htable_size,
&net->ct.hash_vmalloc, 1);
if (!net->ct.hash) {
@@ -1352,6 +1355,10 @@
nf_ct_free_hashtable(net->ct.hash, net->ct.hash_vmalloc,
nf_conntrack_htable_size);
err_hash:
+ kmem_cache_destroy(net->ct.nf_conntrack_cachep);
+err_cache:
+ kfree(net->ct.slabname);
+err_slabname:
free_percpu(net->ct.stat);
err_stat:
return ret;