[Devel] [PATCH 8/8] user ns: implement user ns unshare
Serge E. Hallyn
serue at us.ibm.com
Tue Dec 19 15:01:47 PST 2006
From: Serge E. Hallyn <serue at us.ibm.com>
Subject: [PATCH 8/8] user ns: implement user ns unshare
Implement CLONE_NEWUSER flag useable at clone and unshare.
Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
---
include/linux/sched.h | 1 +
include/linux/user_namespace.h | 10 +++++
kernel/fork.c | 22 ++++++++++--
kernel/nsproxy.c | 2 +
kernel/user_namespace.c | 74 +++++++++++++++++++++++++++++++++++++++-
5 files changed, 102 insertions(+), 7 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 73df38c..55ecf81 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -26,6 +26,7 @@ #define CLONE_CHILD_SETTID 0x01000000 /*
#define CLONE_STOPPED 0x02000000 /* Start in stopped state */
#define CLONE_NEWUTS 0x04000000 /* New utsname group? */
#define CLONE_NEWIPC 0x08000000 /* New ipcs */
+#define CLONE_NEWUSER 0x10000000 /* New user namespace */
/*
* Scheduling policies
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 4ad4c0d..d577ede 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -25,6 +25,7 @@ static inline struct user_namespace *get
}
extern int copy_user_ns(int flags, struct task_struct *tsk);
+extern int unshare_user_ns(unsigned long flags, struct user_namespace **new_user);
extern void free_user_ns(struct kref *kref);
static inline void put_user_ns(struct user_namespace *ns)
@@ -40,6 +41,15 @@ static inline struct user_namespace *get
return NULL;
}
+static inline int unshare_user_ns(unsigned long flags,
+ struct user_namespace **new_user)
+{
+ if (flags & CLONE_NEWUSER)
+ return -EINVAL;
+
+ return 0;
+}
+
static inline int copy_user_ns(int flags, struct task_struct *tsk)
{
return 0;
diff --git a/kernel/fork.c b/kernel/fork.c
index deafa6e..eead517 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -49,6 +49,7 @@ #include <linux/cn_proc.h>
#include <linux/delayacct.h>
#include <linux/taskstats_kern.h>
#include <linux/random.h>
+#include <linux/user_namespace.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1620,6 +1621,7 @@ asmlinkage long sys_unshare(unsigned lon
struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
struct uts_namespace *uts, *new_uts = NULL;
struct ipc_namespace *ipc, *new_ipc = NULL;
+ struct user_namespace *user, *new_user = NULL;
check_unshare_flags(&unshare_flags);
@@ -1627,7 +1629,7 @@ asmlinkage long sys_unshare(unsigned lon
err = -EINVAL;
if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
- CLONE_NEWUTS|CLONE_NEWIPC))
+ CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER))
goto bad_unshare_out;
if ((err = unshare_thread(unshare_flags)))
@@ -1648,18 +1650,20 @@ asmlinkage long sys_unshare(unsigned lon
goto bad_unshare_cleanup_semundo;
if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
goto bad_unshare_cleanup_uts;
+ if ((err = unshare_user_ns(unshare_flags, &new_user)))
+ goto bad_unshare_cleanup_ipc;
- if (new_ns || new_uts || new_ipc) {
+ if (new_ns || new_uts || new_ipc || new_user) {
old_nsproxy = current->nsproxy;
new_nsproxy = dup_namespaces(old_nsproxy);
if (!new_nsproxy) {
err = -ENOMEM;
- goto bad_unshare_cleanup_ipc;
+ goto bad_unshare_cleanup_user;
}
}
if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
- new_uts || new_ipc) {
+ new_uts || new_ipc || new_user) {
task_lock(current);
@@ -1707,12 +1711,22 @@ asmlinkage long sys_unshare(unsigned lon
new_ipc = ipc;
}
+ if (new_user) {
+ user = current->nsproxy->user_ns;
+ current->nsproxy->user_ns = new_user;
+ new_user = user;
+ }
+
task_unlock(current);
}
if (new_nsproxy)
put_nsproxy(new_nsproxy);
+bad_unshare_cleanup_user:
+ if (new_user)
+ put_user_ns(new_user);
+
bad_unshare_cleanup_ipc:
if (new_ipc)
put_ipc_ns(new_ipc);
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index cf43e06..2d9bafb 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -102,7 +102,7 @@ int copy_namespaces(int flags, struct ta
get_nsproxy(old_ns);
- if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
+ if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | CLONE_NEWUSER)))
return 0;
new_ns = clone_namespaces(old_ns);
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 368f8da..d1ce4c1 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -20,17 +20,87 @@ struct user_namespace init_user_ns = {
EXPORT_SYMBOL_GPL(init_user_ns);
#ifdef CONFIG_USER_NS
+/*
+ * Clone a new ns copying an original user ns, setting refcount to 1
+ * @old_ns: namespace to clone
+ * Return NULL on error (failure to kmalloc), new ns otherwise
+ */
+static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
+{
+ struct user_namespace *ns;
+ struct user_struct *new_user;
+ int n;
+
+ ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
+ if (!ns)
+ return NULL;
+
+ kref_init(&ns->kref);
+
+ for(n = 0; n < UIDHASH_SZ; ++n)
+ INIT_LIST_HEAD(ns->uidhash_table + n);
+
+ /* Insert new root user. */
+ ns->root_user = alloc_uid(ns, 0);
+ if (!ns->root_user) {
+ kfree(ns);
+ return NULL;
+ }
+
+ /* Reset current->user with a new one */
+ new_user = alloc_uid(ns, current->uid);
+ if (!new_user) {
+ free_uid(ns->root_user);
+ kfree(ns);
+ return NULL;
+ }
+
+ switch_uid(new_user);
+ return ns;
+}
+
+/*
+ * unshare the current process' user namespace.
+ */
+int unshare_user_ns(unsigned long flags,
+ struct user_namespace **new_user)
+{
+ if (flags & CLONE_NEWUSER) {
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ *new_user = clone_user_ns(current->nsproxy->user_ns);
+ if (!*new_user)
+ return -ENOMEM;
+ }
+
+ return 0;
+}
int copy_user_ns(int flags, struct task_struct *tsk)
{
- struct user_namespace *old_ns = tsk->nsproxy->user_ns;
+ struct user_namespace *new_ns, *old_ns = tsk->nsproxy->user_ns;
int err = 0;
if (!old_ns)
return 0;
get_user_ns(old_ns);
- return err;
+ if (!(flags & CLONE_NEWUSER))
+ return 0;
+ err = -EPERM;
+ if (!capable(CAP_SYS_ADMIN))
+ goto out;
+ err = -ENOMEM;
+ new_ns = clone_user_ns(old_ns);
+ if (!new_ns)
+ goto out;
+
+ tsk->nsproxy->user_ns = new_ns;
+ err = 0;
+out:
+ put_user_ns(old_ns);
+ return 0;
}
void free_user_ns(struct kref *kref)
--
1.4.1
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