netns: fix double free at netns creation
This patch fix a double free when a network namespace fails.
The previous code does a kfree of the net_generic structure when
one of the init subsystem initialization fails.
The 'setup_net' function does kfree(ng) and returns an error.
The caller, 'copy_net_ns', call net_free on error, and this one
calls kfree(net->gen), making this pointer freed twice.
This patch make the code symetric, the net_alloc does the net_generic
allocation and the net_free frees the net_generic.
Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 55151fa..b0767ab 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -32,24 +32,14 @@
{
/* Must be called with net_mutex held */
struct pernet_operations *ops;
- int error;
- struct net_generic *ng;
+ int error = 0;
atomic_set(&net->count, 1);
+
#ifdef NETNS_REFCNT_DEBUG
atomic_set(&net->use_count, 0);
#endif
- error = -ENOMEM;
- ng = kzalloc(sizeof(struct net_generic) +
- INITIAL_NET_GEN_PTRS * sizeof(void *), GFP_KERNEL);
- if (ng == NULL)
- goto out;
-
- ng->len = INITIAL_NET_GEN_PTRS;
- rcu_assign_pointer(net->gen, ng);
-
- error = 0;
list_for_each_entry(ops, &pernet_list, list) {
if (ops->init) {
error = ops->init(net);
@@ -70,7 +60,6 @@
}
rcu_barrier();
- kfree(ng);
goto out;
}
@@ -78,16 +67,43 @@
static struct kmem_cache *net_cachep;
static struct workqueue_struct *netns_wq;
+static struct net_generic *net_alloc_generic(void)
+{
+ struct net_generic *ng;
+ size_t generic_size = sizeof(struct net_generic) +
+ INITIAL_NET_GEN_PTRS * sizeof(void *);
+
+ ng = kzalloc(generic_size, GFP_KERNEL);
+ if (ng)
+ ng->len = INITIAL_NET_GEN_PTRS;
+
+ return ng;
+}
+
static struct net *net_alloc(void)
{
- return kmem_cache_zalloc(net_cachep, GFP_KERNEL);
+ struct net *net = NULL;
+ struct net_generic *ng;
+
+ ng = net_alloc_generic();
+ if (!ng)
+ goto out;
+
+ net = kmem_cache_zalloc(net_cachep, GFP_KERNEL);
+ if (!net)
+ goto out_free;
+
+ rcu_assign_pointer(net->gen, ng);
+out:
+ return net;
+
+out_free:
+ kfree(ng);
+ goto out;
}
static void net_free(struct net *net)
{
- if (!net)
- return;
-
#ifdef NETNS_REFCNT_DEBUG
if (unlikely(atomic_read(&net->use_count) != 0)) {
printk(KERN_EMERG "network namespace not free! Usage: %d\n",
@@ -112,27 +128,28 @@
err = -ENOMEM;
new_net = net_alloc();
if (!new_net)
- goto out;
+ goto out_err;
mutex_lock(&net_mutex);
err = setup_net(new_net);
- if (err)
- goto out_unlock;
-
- rtnl_lock();
- list_add_tail(&new_net->list, &net_namespace_list);
- rtnl_unlock();
-
-
-out_unlock:
+ if (!err) {
+ rtnl_lock();
+ list_add_tail(&new_net->list, &net_namespace_list);
+ rtnl_unlock();
+ }
mutex_unlock(&net_mutex);
+
+ if (err)
+ goto out_free;
out:
put_net(old_net);
- if (err) {
- net_free(new_net);
- new_net = ERR_PTR(err);
- }
return new_net;
+
+out_free:
+ net_free(new_net);
+out_err:
+ new_net = ERR_PTR(err);
+ goto out;
}
static void cleanup_net(struct work_struct *work)
@@ -188,6 +205,7 @@
static int __init net_ns_init(void)
{
+ struct net_generic *ng;
int err;
printk(KERN_INFO "net_namespace: %zd bytes\n", sizeof(struct net));
@@ -202,6 +220,12 @@
panic("Could not create netns workq");
#endif
+ ng = net_alloc_generic();
+ if (!ng)
+ panic("Could not allocate generic netns");
+
+ rcu_assign_pointer(init_net.gen, ng);
+
mutex_lock(&net_mutex);
err = setup_net(&init_net);