proc: Usable inode numbers for the namespace file descriptors.
Assign a unique proc inode to each namespace, and use that
inode number to ensure we only allocate at most one proc
inode for every namespace in proc.
A single proc inode per namespace allows userspace to test
to see if two processes are in the same namespace.
This has been a long requested feature and only blocked because
a naive implementation would put the id in a global space and
would ultimately require having a namespace for the names of
namespaces, making migration and certain virtualization tricks
impossible.
We still don't have per superblock inode numbers for proc, which
appears necessary for application unaware checkpoint/restart and
migrations (if the application is using namespace file descriptors)
but that is now allowd by the design if it becomes important.
I have preallocated the ipc and uts initial proc inode numbers so
their structures can be statically initialized.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 72c8682..cf3386a 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -26,9 +26,16 @@
if (ns == NULL)
return ERR_PTR(-ENOMEM);
+ err = proc_alloc_inum(&ns->proc_inum);
+ if (err) {
+ kfree(ns);
+ return ERR_PTR(err);
+ }
+
atomic_set(&ns->count, 1);
err = mq_init_ns(ns);
if (err) {
+ proc_free_inum(ns->proc_inum);
kfree(ns);
return ERR_PTR(err);
}
@@ -111,6 +118,7 @@
*/
ipcns_notify(IPCNS_REMOVED);
put_user_ns(ns->user_ns);
+ proc_free_inum(ns->proc_inum);
kfree(ns);
}
@@ -172,10 +180,18 @@
return 0;
}
+static unsigned int ipcns_inum(void *vp)
+{
+ struct ipc_namespace *ns = vp;
+
+ return ns->proc_inum;
+}
+
const struct proc_ns_operations ipcns_operations = {
.name = "ipc",
.type = CLONE_NEWIPC,
.get = ipcns_get,
.put = ipcns_put,
.install = ipcns_install,
+ .inum = ipcns_inum,
};
