11 files changed, 137 insertions, 14 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 276ccaa2670c..cab741c2d603 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -8,6 +8,7 @@
 #include <linux/lockdep.h>
 #include <linux/ipc.h>
 #include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>
 
 #define INIT_FDTABLE \
 {                                                       \
@@ -78,6 +79,7 @@ extern struct nsproxy init_nsproxy;
         .uts_ns         = &init_uts_ns,                                 \
         .mnt_ns         = NULL,                                         \
         INIT_IPC_NS(ipc_ns)                                             \
+        .user_ns        = &init_user_ns,                                \
 }
 
 #define INIT_SIGHAND(sighand) {                                         \
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 189e0dc993ab..6d179a397bfb 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -28,6 +28,7 @@ struct nsproxy {
         struct ipc_namespace *ipc_ns;
         struct mnt_namespace *mnt_ns;
         struct pid_namespace *pid_ns;
+        struct user_namespace *user_ns;
 };
 extern struct nsproxy init_nsproxy;
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b579624477f4..c667255d70db 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -287,6 +287,7 @@ extern signed long schedule_timeout_uninterruptible(signed long timeout);
 asmlinkage void schedule(void);
 
 struct nsproxy;
+struct user_namespace;
 
 /* Maximum number of active map areas.. This is a random (large) number */
 #define DEFAULT_MAX_MAP_COUNT   65536
@@ -1408,7 +1409,7 @@ extern struct task_struct *find_task_by_pid_type(int type, int pid);
 extern void __set_special_pids(pid_t session, pid_t pgrp);
 
 /* per-UID process charging. */
-extern struct user_struct * alloc_uid(uid_t);
+extern struct user_struct * alloc_uid(struct user_namespace *, uid_t);
 static inline struct user_struct *get_uid(struct user_struct *u)
 {
         atomic_inc(&u->__count);
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
new file mode 100644
index 000000000000..92a45867ecfb
--- /dev/null
+++ b/include/linux/user_namespace.h
@@ -0,0 +1,57 @@
+#ifndef _LINUX_USER_NAMESPACE_H
+#define _LINUX_USER_NAMESPACE_H
+
+#include <linux/kref.h>
+#include <linux/nsproxy.h>
+#include <linux/sched.h>
+
+#define UIDHASH_BITS    (CONFIG_BASE_SMALL ? 3 : 8)
+#define UIDHASH_SZ      (1 << UIDHASH_BITS)
+
+struct user_namespace {
+        struct kref             kref;
+        struct list_head        uidhash_table[UIDHASH_SZ];
+        struct user_struct      *root_user;
+};
+
+extern struct user_namespace init_user_ns;
+
+#ifdef CONFIG_USER_NS
+
+static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
+{
+        if (ns)
+                kref_get(&ns->kref);
+        return ns;
+}
+
+extern struct user_namespace *copy_user_ns(int flags,
+                                           struct user_namespace *old_ns);
+extern void free_user_ns(struct kref *kref);
+
+static inline void put_user_ns(struct user_namespace *ns)
+{
+        if (ns)
+                kref_put(&ns->kref, free_user_ns);
+}
+
+#else
+
+static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
+{
+        return &init_user_ns;
+}
+
+static inline struct user_namespace *copy_user_ns(int flags,
+                                                  struct user_namespace *old_ns)
+{
+        return NULL;
+}
+
+static inline void put_user_ns(struct user_namespace *ns)
+{
+}
+
+#endif
+
+#endif /* _LINUX_USER_H */
diff --git a/init/Kconfig b/init/Kconfig
index 1e198b8c6936..0b0e29ed82d1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -209,6 +209,15 @@ config TASK_IO_ACCOUNTING
 
           Say N if unsure.
 
+config USER_NS
+        bool "User Namespaces (EXPERIMENTAL)"
+        default n
+        depends on EXPERIMENTAL
+        help
+          Support user namespaces.  This allows containers, i.e.
+          vservers, to use user namespaces to provide different
+          user info for different servers.  If unsure, say N.
+
 config AUDIT
         bool "Auditing support"
         depends on NET
diff --git a/kernel/Makefile b/kernel/Makefile
index fa8efd437afb..2a999836ca18 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -4,7 +4,7 @@
 
 obj-y     = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
             exit.o itimer.o time.o softirq.o resource.o \
-            sysctl.o capability.o ptrace.o timer.o user.o \
+            sysctl.o capability.o ptrace.o timer.o user.o user_namespace.o \
             signal.o sys.o kmod.o workqueue.o pid.o \
             rcupdate.o extable.o params.o posix-timers.o \
             kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
diff --git a/kernel/fork.c b/kernel/fork.c
index 4015912aaac2..13cf0978780a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1002,7 +1002,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         if (atomic_read(&p->user->processes) >=
                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
-                                p->user != &root_user)
+                    p->user != current->nsproxy->user_ns->root_user)
                         goto bad_fork_free;
         }
 
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index e38bed75367d..895e3a3f2044 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -79,8 +79,15 @@ static struct nsproxy *create_new_namespaces(int flags, struct task_struct *tsk,
         if (IS_ERR(new_nsp->pid_ns))
                 goto out_pid;
 
+        new_nsp->user_ns = copy_user_ns(flags, tsk->nsproxy->user_ns);
+        if (IS_ERR(new_nsp->user_ns))
+                goto out_user;
+
         return new_nsp;
 
+out_user:
+        if (new_nsp->pid_ns)
+                put_pid_ns(new_nsp->pid_ns);
 out_pid:
         if (new_nsp->ipc_ns)
                 put_ipc_ns(new_nsp->ipc_ns);
@@ -140,6 +147,8 @@ void free_nsproxy(struct nsproxy *ns)
                 put_ipc_ns(ns->ipc_ns);
         if (ns->pid_ns)
                 put_pid_ns(ns->pid_ns);
+        if (ns->user_ns)
+                put_user_ns(ns->user_ns);
         kfree(ns);
 }
 
diff --git a/kernel/sys.c b/kernel/sys.c
index 872271ccc384..ed92e2f03342 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -35,6 +35,7 @@
 #include <linux/compat.h>
 #include <linux/syscalls.h>
 #include <linux/kprobes.h>
+#include <linux/user_namespace.h>
 
 #include <asm/uaccess.h>
 #include <asm/io.h>
@@ -1078,13 +1079,13 @@ static int set_user(uid_t new_ruid, int dumpclear)
 {
         struct user_struct *new_user;
 
-        new_user = alloc_uid(new_ruid);
+        new_user = alloc_uid(current->nsproxy->user_ns, new_ruid);
         if (!new_user)
                 return -EAGAIN;
 
         if (atomic_read(&new_user->processes) >=
                                 current->signal->rlim[RLIMIT_NPROC].rlim_cur &&
-                        new_user != &root_user) {
+                        new_user != current->nsproxy->user_ns->root_user) {
                 free_uid(new_user);
                 return -EAGAIN;
         }
diff --git a/kernel/user.c b/kernel/user.c
index 4869563080e9..98b82507797a 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -14,20 +14,19 @@
 #include <linux/bitops.h>
 #include <linux/key.h>
 #include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/user_namespace.h>
 
 /*
  * UID task count cache, to get fast user lookup in "alloc_uid"
  * when changing user ID's (ie setuid() and friends).
  */
 
-#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 8)
-#define UIDHASH_SZ              (1 << UIDHASH_BITS)
 #define UIDHASH_MASK            (UIDHASH_SZ - 1)
 #define __uidhashfn(uid)        (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
-#define uidhashentry(uid)       (uidhash_table + __uidhashfn((uid)))
+#define uidhashentry(ns, uid)   ((ns)->uidhash_table + __uidhashfn((uid)))
 
 static struct kmem_cache *uid_cachep;
-static struct list_head uidhash_table[UIDHASH_SZ];
 
 /*
  * The uidhash_lock is mostly taken from process context, but it is
@@ -94,9 +93,10 @@ struct user_struct *find_user(uid_t uid)
 {
         struct user_struct *ret;
         unsigned long flags;
+        struct user_namespace *ns = current->nsproxy->user_ns;
 
         spin_lock_irqsave(&uidhash_lock, flags);
-        ret = uid_hash_find(uid, uidhashentry(uid));
+        ret = uid_hash_find(uid, uidhashentry(ns, uid));
         spin_unlock_irqrestore(&uidhash_lock, flags);
         return ret;
 }
@@ -120,9 +120,9 @@ void free_uid(struct user_struct *up)
         }
 }
 
-struct user_struct * alloc_uid(uid_t uid)
+struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
 {
-        struct list_head *hashent = uidhashentry(uid);
+        struct list_head *hashent = uidhashentry(ns, uid);
         struct user_struct *up;
 
         spin_lock_irq(&uidhash_lock);
@@ -211,11 +211,11 @@ static int __init uid_cache_init(void)
                         0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
 
         for(n = 0; n < UIDHASH_SZ; ++n)
-                INIT_LIST_HEAD(uidhash_table + n);
+                INIT_LIST_HEAD(init_user_ns.uidhash_table + n);
 
         /* Insert the root user immediately (init already runs as root) */
         spin_lock_irq(&uidhash_lock);
-        uid_hash_insert(&root_user, uidhashentry(0));
+        uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
         spin_unlock_irq(&uidhash_lock);
 
         return 0;
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
new file mode 100644
index 000000000000..3d7964209774
--- /dev/null
+++ b/kernel/user_namespace.c
@@ -0,0 +1,43 @@
+/*
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License as
+ *  published by the Free Software Foundation, version 2 of the
+ *  License.
+ */
+
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/nsproxy.h>
+#include <linux/user_namespace.h>
+
+struct user_namespace init_user_ns = {
+        .kref = {
+                .refcount       = ATOMIC_INIT(2),
+        },
+        .root_user = &root_user,
+};
+
+EXPORT_SYMBOL_GPL(init_user_ns);
+
+#ifdef CONFIG_USER_NS
+
+struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
+{
+        struct user_namespace *new_ns;
+
+        BUG_ON(!old_ns);
+        get_user_ns(old_ns);
+
+        new_ns = old_ns;
+        return new_ns;
+}
+
+void free_user_ns(struct kref *kref)
+{
+        struct user_namespace *ns;
+
+        ns = container_of(kref, struct user_namespace, kref);
+        kfree(ns);
+}
+
+#endif /* CONFIG_USER_NS */