[PATCH review 16/16] proc: Usable inode numbers for the namespace file descriptors.

Eric W. Biederman
2012-11-19T15:18:59Z

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>
---
fs/mount.h | 1 +
fs/namespace.c | 14 ++++++++++++++
fs/proc/namespaces.c | 24 ++++++++++++++----------
include/linux/ipc_namespace.h | 2 ++
include/linux/pid_namespace.h | 1 +
include/linux/proc_fs.h | 7 ++++++-
include/linux/user_namespace.h | 1 +
include/linux/utsname.h | 1 +
include/net/net_namespace.h | 2 ++
init/version.c | 2 ++
ipc/msgutil.c | 2 ++
ipc/namespace.c | 16 ++++++++++++++++
kernel/pid.c | 1 +
kernel/pid_namespace.c | 12 ++++++++++++
kernel/user.c | 2 ++
kernel/user_namespace.c | 15 +++++++++++++++
kernel/utsname.c | 17 ++++++++++++++++-
net/core/net_namespace.c | 24 ++++++++++++++++++++++++
18 files changed, 132 insertions(+), 12 deletions(-)

diff --git a/fs/mount.h b/fs/mount.h
index 630fafc..cd50079 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -4,6 +4,7 @@

struct mnt_namespace {
atomic_t count;
+ unsigned int proc_inum;
struct mount * root;
struct list_head list;
struct user_namespace *user_ns;
diff --git a/fs/namespace.c b/fs/namespace.c
index cab78a7..c1bbe86 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2301,6 +2301,7 @@ dput_out:

static void free_mnt_ns(struct mnt_namespace *ns)
{
+ proc_free_inum(ns->proc_inum);
put_user_ns(ns->user_ns);
kfree(ns);
}
@@ -2317,10 +2318,16 @@ static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
{
struct mnt_namespace *new_ns;
+ int ret;

new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
if (!new_ns)
return ERR_PTR(-ENOMEM);
+ ret = proc_alloc_inum(&new_ns->proc_inum);
+ if (ret) {
+ kfree(new_ns);
+ return ERR_PTR(ret);
+ }
new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
atomic_set(&new_ns->count, 1);
new_ns->root = NULL;
@@ -2799,10 +2806,17 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns)
return 0;
}

+static unsigned int mntns_inum(void *ns)
+{
+ struct mnt_namespace *mnt_ns = ns;
+ return mnt_ns->proc_inum;
+}
+
const struct proc_ns_operations mntns_operations = {
.name = "mnt",
.type = CLONE_NEWNS,
.get = mntns_get,
.put = mntns_put,
.install = mntns_install,
+ .inum = mntns_inum,
};
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 7a6d8d6..b7a4719 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -82,7 +82,7 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb,
return ERR_PTR(-ENOMEM);
}

- inode = new_inode(sb);
+ inode = iget_locked(sb, ns_ops->inum(ns));
if (!inode) {
dput(dentry);
ns_ops->put(ns);
@@ -90,13 +90,17 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb,
}

ei = PROC_I(inode);
- inode->i_ino = get_next_ino();
- inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
- inode->i_op = &ns_inode_operations;
- inode->i_mode = S_IFREG | S_IRUGO;
- inode->i_fop = &ns_file_operations;
- ei->ns_ops = ns_ops;
- ei->ns = ns;
+ if (inode->i_state & I_NEW) {
+ inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+ inode->i_op = &ns_inode_operations;
+ inode->i_mode = S_IFREG | S_IRUGO;
+ inode->i_fop = &ns_file_operations;
+ ei->ns_ops = ns_ops;
+ ei->ns = ns;
+ unlock_new_inode(inode);
+ } else {
+ ns_ops->put(ns);
+ }

d_set_d_op(dentry, &ns_dentry_operations);
result = d_instantiate_unique(dentry, inode);
@@ -162,12 +166,12 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
if (!ns)
goto out_put_task;

- snprintf(name, sizeof(name), "%s", ns_ops->name);
+ snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns));
len = strlen(name);

if (len > buflen)
len = buflen;
- if (copy_to_user(buffer, ns_ops->name, len))
+ if (copy_to_user(buffer, name, len))
len = -EFAULT;

ns_ops->put(ns);
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index f03af70..fe77197 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -67,6 +67,8 @@ struct ipc_namespace {

/* user_ns which owns the ipc ns */
struct user_namespace *user_ns;
+
+ unsigned int proc_inum;
};

extern struct ipc_namespace init_ipc_ns;
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 4c96acd..bf28599 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -37,6 +37,7 @@ struct pid_namespace {
kgid_t pid_gid;
int hide_pid;
int reboot; /* group exit code if this pidns was rebooted */
+ unsigned int proc_inum;
};

extern struct pid_namespace init_pid_ns;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index bf1d000..2e24018 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -28,7 +28,11 @@ struct mm_struct;
*/

enum {
- PROC_ROOT_INO = 1,
+ PROC_ROOT_INO = 1,
+ PROC_IPC_INIT_INO = 0xEFFFFFFFU,
+ PROC_UTS_INIT_INO = 0xEFFFFFFEU,
+ PROC_USER_INIT_INO = 0xEFFFFFFDU,
+ PROC_PID_INIT_INO = 0xEFFFFFFCU,
};

/*
@@ -263,6 +267,7 @@ struct proc_ns_operations {
void *(*get)(struct task_struct *task);
void (*put)(void *ns);
int (*install)(struct nsproxy *nsproxy, void *ns);
+ unsigned int (*inum)(void *ns);
};
extern const struct proc_ns_operations netns_operations;
extern const struct proc_ns_operations utsns_operations;
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 17651f0..b9bd2e6 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -25,6 +25,7 @@ struct user_namespace {
struct user_namespace *parent;
kuid_t owner;
kgid_t group;
+ unsigned int proc_inum;
};

extern struct user_namespace init_user_ns;
diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 221f4a0..239e277 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -23,6 +23,7 @@ struct uts_namespace {
struct kref kref;
struct new_utsname name;
struct user_namespace *user_ns;
+ unsigned int proc_inum;
};
extern struct uts_namespace init_uts_ns;

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index c5a43f5..de644bc 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -56,6 +56,8 @@ struct net {

struct user_namespace *user_ns; /* Owning user namespace */

+ unsigned int proc_inum;
+
struct proc_dir_entry *proc_net;
struct proc_dir_entry *proc_net_stat;

diff --git a/init/version.c b/init/version.c
index 86fe0cc..58170f1 100644
--- a/init/version.c
+++ b/init/version.c
@@ -12,6 +12,7 @@
#include <linux/utsname.h>
#include <generated/utsrelease.h>
#include <linux/version.h>
+#include <linux/proc_fs.h>

#ifndef CONFIG_KALLSYMS
#define version(a) Version_ ## a
@@ -34,6 +35,7 @@ struct uts_namespace init_uts_ns = {
.domainname = UTS_DOMAINNAME,
},
.user_ns = &init_user_ns,
+ .proc_inum = PROC_UTS_INIT_INO,
};
EXPORT_SYMBOL_GPL(init_uts_ns);

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index 26143d3..6471f1b 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -16,6 +16,7 @@
#include <linux/msg.h>
#include <linux/ipc_namespace.h>
#include <linux/utsname.h>
+#include <linux/proc_fs.h>
#include <asm/uaccess.h>

#include "util.h"
@@ -30,6 +31,7 @@ DEFINE_SPINLOCK(mq_lock);
struct ipc_namespace init_ipc_ns = {
.count = ATOMIC_INIT(1),
.user_ns = &init_user_ns,
+ .proc_inum = PROC_IPC_INIT_INO,
};

atomic_t nr_ipc_ns = ATOMIC_INIT(1);
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 @@ 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);
kfree(ns);
return ERR_PTR(err);
}
@@ -111,6 +118,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
*/
ipcns_notify(IPCNS_REMOVED);
put_user_ns(ns->user_ns);
+ proc_free_inum(ns->proc_inum);
kfree(ns);
}

@@ -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",
.type = CLONE_NEWIPC,
.get = ipcns_get,
.put = ipcns_put,
.install = ipcns_install,
+ .inum = ipcns_inum,
};
diff --git a/kernel/pid.c b/kernel/pid.c
index 6e8da29..3026dda 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -80,6 +80,7 @@ struct pid_namespace init_pid_ns = {
.level = 0,
.child_reaper = &init_task,
.user_ns = &init_user_ns,
+ .proc_inum = PROC_PID_INIT_INO,
};
EXPORT_SYMBOL_GPL(init_pid_ns);

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 68508d3..560da0d 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;
+
kref_init(&ns->kref);
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++)
kfree(ns->pidmap[i].page);
put_user_ns(ns->user_ns);
@@ -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",
.type = CLONE_NEWPID,
.get = pidns_get,
.put = pidns_put,
.install = pidns_install,
+ .inum = pidns_inum,
};

static __init int pid_namespaces_init(void)
diff --git a/kernel/user.c b/kernel/user.c
index 750acff..33acb5e 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -16,6 +16,7 @@
#include <linux/interrupt.h>
#include <linux/export.h>
#include <linux/user_namespace.h>
+#include <linux/proc_fs.h>

/*
* userns count is 1 for root user, 1 for init_uts_ns,
@@ -51,6 +52,7 @@ struct user_namespace init_user_ns = {
},
.owner = GLOBAL_ROOT_UID,
.group = GLOBAL_ROOT_GID,
+ .proc_inum = PROC_USER_INIT_INO,
};
EXPORT_SYMBOL_GPL(init_user_ns);

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 89f6eae..f5975cc 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)
diff --git a/kernel/utsname.c b/kernel/utsname.c
index fdc619e..f6336d5 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -36,11 +36,18 @@ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
struct uts_namespace *old_ns)
{
struct uts_namespace *ns;
+ int err;

ns = create_uts_ns();
if (!ns)
return ERR_PTR(-ENOMEM);

+ err = proc_alloc_inum(&ns->proc_inum);
+ if (err) {
+ kfree(ns);
+ return ERR_PTR(err);
+ }
+
down_read(&uts_sem);
memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
ns->user_ns = get_user_ns(user_ns);
@@ -77,6 +84,7 @@ void free_uts_ns(struct kref *kref)

ns = container_of(kref, struct uts_namespace, kref);
put_user_ns(ns->user_ns);
+ proc_free_inum(ns->proc_inum);
kfree(ns);
}

@@ -114,11 +122,18 @@ static int utsns_install(struct nsproxy *nsproxy, void *new)
return 0;
}

+static unsigned int utsns_inum(void *vp)
+{
+ struct uts_namespace *ns = vp;
+
+ return ns->proc_inum;
+}
+
const struct proc_ns_operations utsns_operations = {
.name = "uts",
.type = CLONE_NEWUTS,
.get = utsns_get,
.put = utsns_put,
.install = utsns_install,
+ .inum = utsns_inum,
};
-
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index ec2870b..2e9a313 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -381,6 +381,21 @@ struct net *get_net_ns_by_pid(pid_t pid)
}
EXPORT_SYMBOL_GPL(get_net_ns_by_pid);

+static __net_init int net_ns_net_init(struct net *net)
+{
+ return proc_alloc_inum(&net->proc_inum);
+}
+
+static __net_exit void net_ns_net_exit(struct net *net)
+{
+ proc_free_inum(net->proc_inum);
+}
+
+static struct pernet_operations __net_initdata net_ns_ops = {
+ .init = net_ns_net_init,
+ .exit = net_ns_net_exit,
+};
+
static int __init net_ns_init(void)
{
struct net_generic *ng;
@@ -412,6 +427,8 @@ static int __init net_ns_init(void)

mutex_unlock(&net_mutex);

+ register_pernet_subsys(&net_ns_ops);
+
return 0;
}

@@ -640,11 +657,18 @@ static int netns_install(struct nsproxy *nsproxy, void *ns)
return 0;
}

+static unsigned int netns_inum(void *ns)
+{
+ struct net *net = ns;
+ return net->proc_inum;
+}
+
const struct proc_ns_operations netns_operations = {
.name = "net",
.type = CLONE_NEWNET,
.get = netns_get,
.put = netns_put,
.install = netns_install,
+ .inum = netns_inum,
};
#endif
--
1.7.5.4