Merge sys_clone()/sys_unshare() nsproxy and namespace handling

sys_clone() and sys_unshare() both makes copies of nsproxy and its associated
namespaces.  But they have different code paths.

This patch merges all the nsproxy and its associated namespace copy/clone
handling (as much as possible).  Posted on container list earlier for
feedback.

- Create a new nsproxy and its associated namespaces and pass it back to
  caller to attach it to right process.

- Changed all copy_*_ns() routines to return a new copy of namespace
  instead of attaching it to task->nsproxy.

- Moved the CAP_SYS_ADMIN checks out of copy_*_ns() routines.

- Removed unnessary !ns checks from copy_*_ns() and added BUG_ON()
  just incase.

- Get rid of all individual unshare_*_ns() routines and make use of
  copy_*_ns() instead.

[akpm@osdl.org: cleanups, warning fix]
[clg@fr.ibm.com: remove dup_namespaces() declaration]
[serue@us.ibm.com: fix CONFIG_IPC_NS=n, clone(CLONE_NEWIPC) retval]
[akpm@linux-foundation.org: fix build with CONFIG_SYSVIPC=n]
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <containers@lists.osdl.org>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

11 files changed, 131 insertions, 268 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index fd999cab7b57..be5e56bfb73e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1441,10 +1441,9 @@ dput_out:
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
  */
-struct mnt_namespace *dup_mnt_ns(struct task_struct *tsk,
+static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
                 struct fs_struct *fs)
 {
-        struct mnt_namespace *mnt_ns = tsk->nsproxy->mnt_ns;
         struct mnt_namespace *new_ns;
         struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
         struct vfsmount *p, *q;
@@ -1509,36 +1508,21 @@ struct mnt_namespace *dup_mnt_ns(struct task_struct *tsk,
         return new_ns;
 }
 
-int copy_mnt_ns(int flags, struct task_struct *tsk)
+struct mnt_namespace *copy_mnt_ns(int flags, struct mnt_namespace *ns,
+                struct fs_struct *new_fs)
 {
-        struct mnt_namespace *ns = tsk->nsproxy->mnt_ns;
         struct mnt_namespace *new_ns;
-        int err = 0;
-
-        if (!ns)
-                return 0;
 
+        BUG_ON(!ns);
         get_mnt_ns(ns);
 
         if (!(flags & CLONE_NEWNS))
-                return 0;
-
-        if (!capable(CAP_SYS_ADMIN)) {
-                err = -EPERM;
-                goto out;
-        }
-
-        new_ns = dup_mnt_ns(tsk, tsk->fs);
-        if (!new_ns) {
-                err = -ENOMEM;
-                goto out;
-        }
+                return ns;
 
-        tsk->nsproxy->mnt_ns = new_ns;
+        new_ns = dup_mnt_ns(ns, new_fs);
 
-out:
         put_mnt_ns(ns);
-        return err;
+        return new_ns;
 }
 
 asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
diff --git a/include/linux/ipc.h b/include/linux/ipc.h
index 6da6772c19ff..1980867a64a4 100644
--- a/include/linux/ipc.h
+++ b/include/linux/ipc.h
@@ -92,16 +92,19 @@ extern struct ipc_namespace init_ipc_ns;
 
 #ifdef CONFIG_SYSVIPC
 #define INIT_IPC_NS(ns)         .ns             = &init_ipc_ns,
-extern int copy_ipcs(unsigned long flags, struct task_struct *tsk);
+extern struct ipc_namespace *copy_ipcs(unsigned long flags,
+                                                struct ipc_namespace *ns);
 #else
 #define INIT_IPC_NS(ns)
-static inline int copy_ipcs(unsigned long flags, struct task_struct *tsk)
-{ return 0; }
+static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
+                                                struct ipc_namespace *ns)
+{
+        return ns;
+}
 #endif
 
 #ifdef CONFIG_IPC_NS
 extern void free_ipc_ns(struct kref *kref);
-extern int unshare_ipcs(unsigned long flags, struct ipc_namespace **ns);
 #endif
 
 static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 4af0b1fc282a..1fa4d9813b31 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -14,10 +14,9 @@ struct mnt_namespace {
         int event;
 };
 
-extern int copy_mnt_ns(int, struct task_struct *);
-extern void __put_mnt_ns(struct mnt_namespace *ns);
-extern struct mnt_namespace *dup_mnt_ns(struct task_struct *,
+extern struct mnt_namespace *copy_mnt_ns(int, struct mnt_namespace *,
                 struct fs_struct *);
+extern void __put_mnt_ns(struct mnt_namespace *ns);
 
 static inline void put_mnt_ns(struct mnt_namespace *ns)
 {
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 0b9f0dc30d61..189e0dc993ab 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -31,10 +31,11 @@ struct nsproxy {
 };
 extern struct nsproxy init_nsproxy;
 
-struct nsproxy *dup_namespaces(struct nsproxy *orig);
 int copy_namespaces(int flags, struct task_struct *tsk);
 void get_task_namespaces(struct task_struct *tsk);
 void free_nsproxy(struct nsproxy *ns);
+int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
+        struct fs_struct *);
 
 static inline void put_nsproxy(struct nsproxy *ns)
 {
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 2833806d42c6..169c6c24209b 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -29,7 +29,7 @@ static inline void get_pid_ns(struct pid_namespace *ns)
         kref_get(&ns->kref);
 }
 
-extern int copy_pid_ns(int flags, struct task_struct *tsk);
+extern struct pid_namespace *copy_pid_ns(int flags, struct pid_namespace *ns);
 extern void free_pid_ns(struct kref *kref);
 
 static inline void put_pid_ns(struct pid_namespace *ns)
diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index e10267d402c5..f8d3b326e93a 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -49,9 +49,7 @@ static inline void get_uts_ns(struct uts_namespace *ns)
 }
 
 #ifdef CONFIG_UTS_NS
-extern int unshare_utsname(unsigned long unshare_flags,
-                                struct uts_namespace **new_uts);
-extern int copy_utsname(int flags, struct task_struct *tsk);
+extern struct uts_namespace *copy_utsname(int flags, struct uts_namespace *ns);
 extern void free_uts_ns(struct kref *kref);
 
 static inline void put_uts_ns(struct uts_namespace *ns)
@@ -59,21 +57,12 @@ static inline void put_uts_ns(struct uts_namespace *ns)
         kref_put(&ns->kref, free_uts_ns);
 }
 #else
-static inline int unshare_utsname(unsigned long unshare_flags,
-                        struct uts_namespace **new_uts)
+static inline struct uts_namespace *copy_utsname(int flags,
+                                                struct uts_namespace *ns)
 {
-        if (unshare_flags & CLONE_NEWUTS)
-                return -EINVAL;
-
-        return 0;
+        return ns;
 }
 
-static inline int copy_utsname(int flags, struct task_struct *tsk)
-{
-        if (flags & CLONE_NEWUTS)
-                return -EINVAL;
-        return 0;
-}
 static inline void put_uts_ns(struct uts_namespace *ns)
 {
 }
diff --git a/ipc/util.c b/ipc/util.c
index 0b652387d169..0ad5b1c3ca01 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -85,53 +85,20 @@ err_mem:
         return ERR_PTR(err);
 }
 
-int unshare_ipcs(unsigned long unshare_flags, struct ipc_namespace **new_ipc)
+struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
 {
-        struct ipc_namespace *new;
-
-        if (unshare_flags & CLONE_NEWIPC) {
-                if (!capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-
-                new = clone_ipc_ns(current->nsproxy->ipc_ns);
-                if (IS_ERR(new))
-                        return PTR_ERR(new);
-
-                *new_ipc = new;
-        }
-
-        return 0;
-}
-
-int copy_ipcs(unsigned long flags, struct task_struct *tsk)
-{
-        struct ipc_namespace *old_ns = tsk->nsproxy->ipc_ns;
         struct ipc_namespace *new_ns;
-        int err = 0;
 
-        if (!old_ns)
-                return 0;
-
-        get_ipc_ns(old_ns);
+        BUG_ON(!ns);
+        get_ipc_ns(ns);
 
         if (!(flags & CLONE_NEWIPC))
-                return 0;
+                return ns;
 
-        if (!capable(CAP_SYS_ADMIN)) {
-                err = -EPERM;
-                goto out;
-        }
+        new_ns = clone_ipc_ns(ns);
 
-        new_ns = clone_ipc_ns(old_ns);
-        if (!new_ns) {
-                err = -ENOMEM;
-                goto out;
-        }
-
-        tsk->nsproxy->ipc_ns = new_ns;
-out:
-        put_ipc_ns(old_ns);
-        return err;
+        put_ipc_ns(ns);
+        return new_ns;
 }
 
 void free_ipc_ns(struct kref *kref)
@@ -145,11 +112,11 @@ void free_ipc_ns(struct kref *kref)
         kfree(ns);
 }
 #else
-int copy_ipcs(unsigned long flags, struct task_struct *tsk)
+struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
 {
         if (flags & CLONE_NEWIPC)
-                return -EINVAL;
-        return 0;
+                return ERR_PTR(-EINVAL);
+        return ns;
 }
 #endif
 
diff --git a/kernel/fork.c b/kernel/fork.c
index b7d169def942..fd211b9dddd4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1516,26 +1516,6 @@ static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
 }
 
 /*
- * Unshare the mnt_namespace structure if it is being shared
- */
-static int unshare_mnt_namespace(unsigned long unshare_flags,
-                struct mnt_namespace **new_nsp, struct fs_struct *new_fs)
-{
-        struct mnt_namespace *ns = current->nsproxy->mnt_ns;
-
-        if ((unshare_flags & CLONE_NEWNS) && ns) {
-                if (!capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-
-                *new_nsp = dup_mnt_ns(current, new_fs ? new_fs : current->fs);
-                if (!*new_nsp)
-                        return -ENOMEM;
-        }
-
-        return 0;
-}
-
-/*
  * Unsharing of sighand is not supported yet
  */
 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
@@ -1593,16 +1573,6 @@ static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **n
         return 0;
 }
 
-#ifndef CONFIG_IPC_NS
-static inline int unshare_ipcs(unsigned long flags, struct ipc_namespace **ns)
-{
-        if (flags & CLONE_NEWIPC)
-                return -EINVAL;
-
-        return 0;
-}
-#endif
-
 /*
  * unshare allows a process to 'unshare' part of the process
  * context which was originally shared using clone.  copy_*
@@ -1615,14 +1585,11 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
 {
         int err = 0;
         struct fs_struct *fs, *new_fs = NULL;
-        struct mnt_namespace *ns, *new_ns = NULL;
         struct sighand_struct *new_sigh = NULL;
         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
         struct files_struct *fd, *new_fd = NULL;
         struct sem_undo_list *new_ulist = NULL;
         struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
-        struct uts_namespace *uts, *new_uts = NULL;
-        struct ipc_namespace *ipc, *new_ipc = NULL;
 
         check_unshare_flags(&unshare_flags);
 
@@ -1637,36 +1604,24 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
                 goto bad_unshare_out;
         if ((err = unshare_fs(unshare_flags, &new_fs)))
                 goto bad_unshare_cleanup_thread;
-        if ((err = unshare_mnt_namespace(unshare_flags, &new_ns, new_fs)))
-                goto bad_unshare_cleanup_fs;
         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
-                goto bad_unshare_cleanup_ns;
+                goto bad_unshare_cleanup_fs;
         if ((err = unshare_vm(unshare_flags, &new_mm)))
                 goto bad_unshare_cleanup_sigh;
         if ((err = unshare_fd(unshare_flags, &new_fd)))
                 goto bad_unshare_cleanup_vm;
         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
                 goto bad_unshare_cleanup_fd;
-        if ((err = unshare_utsname(unshare_flags, &new_uts)))
+        if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
+                        new_fs)))
                 goto bad_unshare_cleanup_semundo;
-        if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
-                goto bad_unshare_cleanup_uts;
-
-        if (new_ns || new_uts || new_ipc) {
-                old_nsproxy = current->nsproxy;
-                new_nsproxy = dup_namespaces(old_nsproxy);
-                if (!new_nsproxy) {
-                        err = -ENOMEM;
-                        goto bad_unshare_cleanup_ipc;
-                }
-        }
 
-        if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
-                                new_uts || new_ipc) {
+        if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
 
                 task_lock(current);
 
                 if (new_nsproxy) {
+                        old_nsproxy = current->nsproxy;
                         current->nsproxy = new_nsproxy;
                         new_nsproxy = old_nsproxy;
                 }
@@ -1677,12 +1632,6 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
                         new_fs = fs;
                 }
 
-                if (new_ns) {
-                        ns = current->nsproxy->mnt_ns;
-                        current->nsproxy->mnt_ns = new_ns;
-                        new_ns = ns;
-                }
-
                 if (new_mm) {
                         mm = current->mm;
                         active_mm = current->active_mm;
@@ -1698,32 +1647,12 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
                         new_fd = fd;
                 }
 
-                if (new_uts) {
-                        uts = current->nsproxy->uts_ns;
-                        current->nsproxy->uts_ns = new_uts;
-                        new_uts = uts;
-                }
-
-                if (new_ipc) {
-                        ipc = current->nsproxy->ipc_ns;
-                        current->nsproxy->ipc_ns = new_ipc;
-                        new_ipc = ipc;
-                }
-
                 task_unlock(current);
         }
 
         if (new_nsproxy)
                 put_nsproxy(new_nsproxy);
 
-bad_unshare_cleanup_ipc:
-        if (new_ipc)
-                put_ipc_ns(new_ipc);
-
-bad_unshare_cleanup_uts:
-        if (new_uts)
-                put_uts_ns(new_uts);
-
 bad_unshare_cleanup_semundo:
 bad_unshare_cleanup_fd:
         if (new_fd)
@@ -1738,10 +1667,6 @@ bad_unshare_cleanup_sigh:
                 if (atomic_dec_and_test(&new_sigh->count))
                         kmem_cache_free(sighand_cachep, new_sigh);
 
-bad_unshare_cleanup_ns:
-        if (new_ns)
-                put_mnt_ns(new_ns);
-
 bad_unshare_cleanup_fs:
         if (new_fs)
                 put_fs_struct(new_fs);
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f5b9ee6f6bbb..1bc4b55241a8 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -38,10 +38,8 @@ void get_task_namespaces(struct task_struct *tsk)
 
 /*
  * creates a copy of "orig" with refcount 1.
- * This does not grab references to the contained namespaces,
- * so that needs to be done by dup_namespaces.
  */
-static inline struct nsproxy *clone_namespaces(struct nsproxy *orig)
+static inline struct nsproxy *clone_nsproxy(struct nsproxy *orig)
 {
         struct nsproxy *ns;
 
@@ -52,26 +50,49 @@ static inline struct nsproxy *clone_namespaces(struct nsproxy *orig)
 }
 
 /*
- * copies the nsproxy, setting refcount to 1, and grabbing a
- * reference to all contained namespaces.  Called from
- * sys_unshare()
+ * Create new nsproxy and all of its the associated namespaces.
+ * Return the newly created nsproxy.  Do not attach this to the task,
+ * leave it to the caller to do proper locking and attach it to task.
  */
-struct nsproxy *dup_namespaces(struct nsproxy *orig)
+static struct nsproxy *create_new_namespaces(int flags, struct task_struct *tsk,
+                        struct fs_struct *new_fs)
 {
-        struct nsproxy *ns = clone_namespaces(orig);
+        struct nsproxy *new_nsp;
 
-        if (ns) {
-                if (ns->mnt_ns)
-                        get_mnt_ns(ns->mnt_ns);
-                if (ns->uts_ns)
-                        get_uts_ns(ns->uts_ns);
-                if (ns->ipc_ns)
-                        get_ipc_ns(ns->ipc_ns);
-                if (ns->pid_ns)
-                        get_pid_ns(ns->pid_ns);
-        }
+        new_nsp = clone_nsproxy(tsk->nsproxy);
+        if (!new_nsp)
+                return ERR_PTR(-ENOMEM);
 
-        return ns;
+        new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, new_fs);
+        if (IS_ERR(new_nsp->mnt_ns))
+                goto out_ns;
+
+        new_nsp->uts_ns = copy_utsname(flags, tsk->nsproxy->uts_ns);
+        if (IS_ERR(new_nsp->uts_ns))
+                goto out_uts;
+
+        new_nsp->ipc_ns = copy_ipcs(flags, tsk->nsproxy->ipc_ns);
+        if (IS_ERR(new_nsp->ipc_ns))
+                goto out_ipc;
+
+        new_nsp->pid_ns = copy_pid_ns(flags, tsk->nsproxy->pid_ns);
+        if (IS_ERR(new_nsp->pid_ns))
+                goto out_pid;
+
+        return new_nsp;
+
+out_pid:
+        if (new_nsp->ipc_ns)
+                put_ipc_ns(new_nsp->ipc_ns);
+out_ipc:
+        if (new_nsp->uts_ns)
+                put_uts_ns(new_nsp->uts_ns);
+out_uts:
+        if (new_nsp->mnt_ns)
+                put_mnt_ns(new_nsp->mnt_ns);
+out_ns:
+        kfree(new_nsp);
+        return ERR_PTR(-ENOMEM);
 }
 
 /*
@@ -92,47 +113,21 @@ int copy_namespaces(int flags, struct task_struct *tsk)
         if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
                 return 0;
 
-        new_ns = clone_namespaces(old_ns);
-        if (!new_ns) {
-                err = -ENOMEM;
+        if (!capable(CAP_SYS_ADMIN)) {
+                err = -EPERM;
                 goto out;
         }
 
-        tsk->nsproxy = new_ns;
-
-        err = copy_mnt_ns(flags, tsk);
-        if (err)
-                goto out_ns;
-
-        err = copy_utsname(flags, tsk);
-        if (err)
-                goto out_uts;
-
-        err = copy_ipcs(flags, tsk);
-        if (err)
-                goto out_ipc;
-
-        err = copy_pid_ns(flags, tsk);
-        if (err)
-                goto out_pid;
+        new_ns = create_new_namespaces(flags, tsk, tsk->fs);
+        if (IS_ERR(new_ns)) {
+                err = PTR_ERR(new_ns);
+                goto out;
+        }
 
+        tsk->nsproxy = new_ns;
 out:
         put_nsproxy(old_ns);
         return err;
-
-out_pid:
-        if (new_ns->ipc_ns)
-                put_ipc_ns(new_ns->ipc_ns);
-out_ipc:
-        if (new_ns->uts_ns)
-                put_uts_ns(new_ns->uts_ns);
-out_uts:
-        if (new_ns->mnt_ns)
-                put_mnt_ns(new_ns->mnt_ns);
-out_ns:
-        tsk->nsproxy = old_ns;
-        kfree(new_ns);
-        goto out;
 }
 
 void free_nsproxy(struct nsproxy *ns)
@@ -147,3 +142,41 @@ void free_nsproxy(struct nsproxy *ns)
                 put_pid_ns(ns->pid_ns);
         kfree(ns);
 }
+
+/*
+ * Called from unshare. Unshare all the namespaces part of nsproxy.
+ * On sucess, returns the new nsproxy and a reference to old nsproxy
+ * to make sure it stays around.
+ */
+int unshare_nsproxy_namespaces(unsigned long unshare_flags,
+                struct nsproxy **new_nsp, struct fs_struct *new_fs)
+{
+        struct nsproxy *old_ns = current->nsproxy;
+        int err = 0;
+
+        if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
+                return 0;
+
+#ifndef CONFIG_IPC_NS
+        if (unshare_flags & CLONE_NEWIPC)
+                return -EINVAL;
+#endif
+
+#ifndef CONFIG_UTS_NS
+        if (unshare_flags & CLONE_NEWUTS)
+                return -EINVAL;
+#endif
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        get_nsproxy(old_ns);
+
+        *new_nsp = create_new_namespaces(unshare_flags, current,
+                                new_fs ? new_fs : current->fs);
+        if (IS_ERR(*new_nsp)) {
+                err = PTR_ERR(*new_nsp);
+                put_nsproxy(old_ns);
+        }
+        return err;
+}
diff --git a/kernel/pid.c b/kernel/pid.c
index 9c80bc23d6b8..d3ad724afa83 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -360,16 +360,11 @@ struct pid *find_ge_pid(int nr)
 }
 EXPORT_SYMBOL_GPL(find_get_pid);
 
-int copy_pid_ns(int flags, struct task_struct *tsk)
+struct pid_namespace *copy_pid_ns(int flags, struct pid_namespace *old_ns)
 {
-        struct pid_namespace *old_ns = tsk->nsproxy->pid_ns;
-        int err = 0;
-
-        if (!old_ns)
-                return 0;
-
+        BUG_ON(!old_ns);
         get_pid_ns(old_ns);
-        return err;
+        return old_ns;
 }
 
 void free_pid_ns(struct kref *kref)
diff --git a/kernel/utsname.c b/kernel/utsname.c
index c859164a6993..160c8c5136bd 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -32,58 +32,25 @@ static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
 }
 
 /*
- * unshare the current process' utsname namespace.
- * called only in sys_unshare()
- */
-int unshare_utsname(unsigned long unshare_flags, struct uts_namespace **new_uts)
-{
-        if (unshare_flags & CLONE_NEWUTS) {
-                if (!capable(CAP_SYS_ADMIN))
-                        return -EPERM;
-
-                *new_uts = clone_uts_ns(current->nsproxy->uts_ns);
-                if (!*new_uts)
-                        return -ENOMEM;
-        }
-
-        return 0;
-}
-
-/*
  * Copy task tsk's utsname namespace, or clone it if flags
  * specifies CLONE_NEWUTS.  In latter case, changes to the
  * utsname of this process won't be seen by parent, and vice
  * versa.
  */
-int copy_utsname(int flags, struct task_struct *tsk)
+struct uts_namespace *copy_utsname(int flags, struct uts_namespace *old_ns)
 {
-        struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
         struct uts_namespace *new_ns;
-        int err = 0;
-
-        if (!old_ns)
-                return 0;
 
+        BUG_ON(!old_ns);
         get_uts_ns(old_ns);
 
         if (!(flags & CLONE_NEWUTS))
-                return 0;
-
-        if (!capable(CAP_SYS_ADMIN)) {
-                err = -EPERM;
-                goto out;
-        }
+                return old_ns;
 
         new_ns = clone_uts_ns(old_ns);
-        if (!new_ns) {
-                err = -ENOMEM;
-                goto out;
-        }
-        tsk->nsproxy->uts_ns = new_ns;
 
-out:
         put_uts_ns(old_ns);
-        return err;
+        return new_ns;
 }
 
 void free_uts_ns(struct kref *kref)