path: root/kernel/pid_namespace.c
diff options
authorEric W. Biederman <ebiederm@xmission.com>2011-06-15 10:21:48 -0700
committerEric W. Biederman <ebiederm@xmission.com>2012-11-20 04:19:49 -0800
commit98f842e675f96ffac96e6c50315790912b2812be (patch)
treeed4dee9a6e54e3443e9f3f1614c8a2fcf9b31e0a /kernel/pid_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 <ebiederm@xmission.com>
Diffstat (limited to 'kernel/pid_namespace.c')
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 68508d33063..560da0dab23 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -107,6 +107,10 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
if (ns->pid_cachep == NULL)
goto out_free_map;
+ err = proc_alloc_inum(&ns->proc_inum);
+ if (err)
+ goto out_free_map;
ns->level = level;
ns->parent = get_pid_ns(parent_pid_ns);
@@ -133,6 +137,7 @@ static void destroy_pid_namespace(struct pid_namespace *ns)
int i;
+ proc_free_inum(ns->proc_inum);
for (i = 0; i < PIDMAP_ENTRIES; i++)
@@ -345,12 +350,19 @@ static int pidns_install(struct nsproxy *nsproxy, void *ns)
return 0;
+static unsigned int pidns_inum(void *ns)
+ struct pid_namespace *pid_ns = ns;
+ return pid_ns->proc_inum;
const struct proc_ns_operations pidns_operations = {
.name = "pid",
.get = pidns_get,
.put = pidns_put,
.install = pidns_install,
+ .inum = pidns_inum,
static __init int pid_namespaces_init(void)