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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/user_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/user_namespace.c')
-rw-r--r--kernel/user_namespace.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 89f6eaed067a..f5975ccf9348 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -58,6 +58,7 @@ int create_user_ns(struct cred *new)
struct user_namespace *ns, *parent_ns = new->user_ns;
kuid_t owner = new->euid;
kgid_t group = new->egid;
+ int ret;
/* The creator needs a mapping in the parent user namespace
* or else we won't be able to reasonably tell userspace who
@@ -71,6 +72,12 @@ int create_user_ns(struct cred *new)
if (!ns)
return -ENOMEM;
+ ret = proc_alloc_inum(&ns->proc_inum);
+ if (ret) {
+ kmem_cache_free(user_ns_cachep, ns);
+ return ret;
+ }
+
kref_init(&ns->kref);
/* Leave the new->user_ns reference with the new user namespace. */
ns->parent = parent_ns;
@@ -103,6 +110,7 @@ void free_user_ns(struct kref *kref)
container_of(kref, struct user_namespace, kref);
parent = ns->parent;
+ proc_free_inum(ns->proc_inum);
kmem_cache_free(user_ns_cachep, ns);
put_user_ns(parent);
}
@@ -808,12 +816,19 @@ static int userns_install(struct nsproxy *nsproxy, void *ns)
return commit_creds(cred);
}
+static unsigned int userns_inum(void *ns)
+{
+ struct user_namespace *user_ns = ns;
+ return user_ns->proc_inum;
+}
+
const struct proc_ns_operations userns_operations = {
.name = "user",
.type = CLONE_NEWUSER,
.get = userns_get,
.put = userns_put,
.install = userns_install,
+ .inum = userns_inum,
};
static __init int user_namespaces_init(void)