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| author | Eric W. Biederman <ebiederm@xmission.com> | 2011-06-15 10:21:48 -0700 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2012-11-20 04:19:49 -0800 |
| commit | 98f842e675f96ffac96e6c50315790912b2812be (patch) | |
| tree | ed4dee9a6e54e3443e9f3f1614c8a2fcf9b31e0a /kernel/user_namespace.c | |
| parent | bf056bfa80596a5d14b26b17276a56a0dcb080e5 (diff) | |
| download | linux-98f842e675f96ffac96e6c50315790912b2812be.tar.bz2 | |
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.c | 15 |
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) |