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[PATCH 1/6] user namespace : add the framework [message #13756 is a reply to message #13755] Mon, 04 June 2007 19:40 Go to previous messageGo to previous message
serue is currently offline  serue
Messages: 750
Registered: February 2006
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>From nobody Mon Sep 17 00:00:00 2001
From: Cedric Le Goater <clg@fr.ibm.com>
Date: Thu, 5 Apr 2007 12:51:51 -0400
Subject: [PATCH 1/6] user namespace : add the framework

Add the user namespace struct and framework

Basically, it will allow a process to unshare its user_struct table, resetting
at the same time its own user_struct and all the associated accounting.

A new root user (uid == 0) is added to the user namespace upon creation. Such
root users have full privileges and it seems that theses privileges should be
controlled through some means (process capabilities ?)

The unshare is not included in this patch.

Changes since [try #4]:
- Updated get_user_ns and put_user_ns to accept NULL, and
get_user_ns to return the namespace.

Changes since [try #3]:
- moved struct user_namespace to files user_namespace.{c,h}

Changes since [try #2]:
- removed struct user_namespace* argument from find_user()

Changes since [try #1]:
- removed struct user_namespace* argument from find_user()
- added a root_user per user namespace

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>

---

include/linux/init_task.h | 2 +
include/linux/nsproxy.h | 1 +
include/linux/sched.h | 3 +-
include/linux/user_namespace.h | 57 ++++++++++++++++++++++++++++++++++++++++
init/Kconfig | 9 ++++++
kernel/Makefile | 2 +
kernel/fork.c | 2 +
kernel/nsproxy.c | 10 +++++++
kernel/sys.c | 5 ++--
kernel/user.c | 18 ++++++-------
kernel/user_namespace.c | 43 ++++++++++++++++++++++++++++++
11 files changed, 138 insertions(+), 14 deletions(-)
create mode 100644 include/linux/user_namespace.h
create mode 100644 kernel/user_namespace.c

cfeebe74a11622089791ecb14070f4d620f55535
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index cca7bb1..1fdc46c 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -8,6 +8,7 @@ #include <linux/utsname.h>
#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 @@ #define INIT_NSPROXY(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 616a710..36e84e5 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 8016ec8..259d0a5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -263,6 +263,7 @@ extern signed long schedule_timeout_unin
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
@@ -1311,7 +1312,7 @@ extern struct task_struct *find_task_by_
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 0000000..c2debd8
--- /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 0;
+}
+
+static inline void put_user_ns(struct user_namespace *ns)
+{
+}
+
+#endif
+
+#endif /* _LINUX_USER_H */
diff --git a/init/Kconfig b/init/Kconfig
index 99b0b32..0bbf957 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -229,6 +229,15 @@ 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 6101981..b5cef19 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 timer.o user.o \
+ sysctl.o capability.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 6ebd35b..c20137e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -999,7 +999,7 @@ #endif
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 3f3b7ad..1ea8a73 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -83,8 +83,15 @@ static struct nsproxy *create_new_namesp
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);
@@ -144,6 +151,9 @@ 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);
+
kmem_cache_free(nsproxy_cachep, ns);
}

diff --git a/kernel/sys.c b/kernel/sys.c
index 7d79146..bb37fcb 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -34,6 +34,7 @@ #include <linux/task_io_accounting_ops.h
#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>
@@ -1077,13 +1078,13 @@ static int set_user(uid_t new_ruid, int
{
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 4869563..98b8250 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -14,20 +14,19 @@ #include <linux/slab.h>
#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 use ...

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