#include <linux/rcupdate.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
#include "util.h"
-static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
+static struct ipc_namespace *create_ipc_ns(void)
{
struct ipc_namespace *ns;
+ int err;
ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
if (ns == NULL)
return ERR_PTR(-ENOMEM);
+ atomic_set(&ns->count, 1);
+ err = mq_init_ns(ns);
+ if (err) {
+ kfree(ns);
+ return ERR_PTR(err);
+ }
atomic_inc(&nr_ipc_ns);
sem_init_ns(ns);
ipcns_notify(IPCNS_CREATED);
register_ipcns_notifier(ns);
- kref_init(&ns->kref);
return ns;
}
struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
{
- struct ipc_namespace *new_ns;
-
- BUG_ON(!ns);
- get_ipc_ns(ns);
-
if (!(flags & CLONE_NEWIPC))
- return ns;
-
- new_ns = clone_ipc_ns(ns);
-
- put_ipc_ns(ns);
- return new_ns;
+ return get_ipc_ns(ns);
+ return create_ipc_ns();
}
/*
up_write(&ids->rw_mutex);
}
-void free_ipc_ns(struct kref *kref)
+static void free_ipc_ns(struct ipc_namespace *ns)
{
- struct ipc_namespace *ns;
-
- ns = container_of(kref, struct ipc_namespace, kref);
/*
* Unregistering the hotplug notifier at the beginning guarantees
* that the ipc namespace won't be freed while we are inside the
*/
ipcns_notify(IPCNS_REMOVED);
}
+
+/*
+ * put_ipc_ns - drop a reference to an ipc namespace.
+ * @ns: the namespace to put
+ *
+ * If this is the last task in the namespace exiting, and
+ * it is dropping the refcount to 0, then it can race with
+ * a task in another ipc namespace but in a mounts namespace
+ * which has this ipcns's mqueuefs mounted, doing some action
+ * with one of the mqueuefs files. That can raise the refcount.
+ * So dropping the refcount, and raising the refcount when
+ * accessing it through the VFS, are protected with mq_lock.
+ *
+ * (Clearly, a task raising the refcount on its own ipc_ns
+ * needn't take mq_lock since it can't race with the last task
+ * in the ipcns exiting).
+ */
+void put_ipc_ns(struct ipc_namespace *ns)
+{
+ if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
+ mq_clear_sbinfo(ns);
+ spin_unlock(&mq_lock);
+ mq_put_mnt(ns);
+ free_ipc_ns(ns);
+ }
+}