path: root/ipc/namespace.c
diff options
authorEric W. Biederman <>2011-06-15 10:21:48 -0700
committerEric W. Biederman <>2012-11-20 04:19:49 -0800
commit98f842e675f96ffac96e6c50315790912b2812be (patch)
treeed4dee9a6e54e3443e9f3f1614c8a2fcf9b31e0a /ipc/namespace.c
parentbf056bfa80596a5d14b26b17276a56a0dcb080e5 (diff)
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 <>
Diffstat (limited to 'ipc/namespace.c')
1 files changed, 16 insertions, 0 deletions
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 72c868277793..cf3386a51de2 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -26,9 +26,16 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
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);
return ERR_PTR(err);
@@ -111,6 +118,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
+ proc_free_inum(ns->proc_inum);
@@ -172,10 +180,18 @@ static int ipcns_install(struct nsproxy *nsproxy, void *new)
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",
.get = ipcns_get,
.put = ipcns_put,
.install = ipcns_install,
+ .inum = ipcns_inum,