From: "Serge E. Hallyn" Quoting Frederik Deweerdt (deweerdt@free.fr): > On Thu, Jan 04, 2007 at 12:13:10PM -0600, Serge E. Hallyn wrote: > > From: Serge E. Hallyn > > Subject: [PATCH -mm 8/8] user ns: implement user ns unshare > > > > Implement CLONE_NEWUSER flag useable at clone/unshare. > > > > Signed-off-by: Serge E. Hallyn > > --- > > > 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; > ^^^^^^^^^^^^ > The "= 0" is superfluous here. Ah, since I set it anyway, good point. > > > > 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; > ^^^^^^^^^ > Should be "return err;" Yes it should. New patch attached. (I suppose the testcase should check for the CAP_SYS_ADMIN error case...) Thanks for the close review! -serge From: Serge E. Hallyn Subject: [PATCH 8/8] user ns: implement user ns unshare Implement CLONE_NEWUSER flag useable at clone/unshare. Changes: Jan 4: return the actual error value in copy_user_ns(). Signed-off-by: Serge E. Hallyn Cc: Herbert Poetzl Cc: Kirill Korotaev Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton --- 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 -puN include/linux/sched.h~user-ns-implement-user-ns-unshare include/linux/sched.h --- a/include/linux/sched.h~user-ns-implement-user-ns-unshare +++ a/include/linux/sched.h @@ -26,6 +26,7 @@ #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 -puN include/linux/user_namespace.h~user-ns-implement-user-ns-unshare include/linux/user_namespace.h --- a/include/linux/user_namespace.h~user-ns-implement-user-ns-unshare +++ a/include/linux/user_namespace.h @@ -26,6 +26,7 @@ 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) @@ -51,6 +52,15 @@ 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 -puN kernel/fork.c~user-ns-implement-user-ns-unshare kernel/fork.c --- a/kernel/fork.c~user-ns-implement-user-ns-unshare +++ a/kernel/fork.c @@ -49,6 +49,7 @@ #include #include #include +#include #include #include @@ -1623,6 +1624,7 @@ 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); @@ -1630,7 +1632,7 @@ 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))) @@ -1651,18 +1653,20 @@ 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); @@ -1710,12 +1714,22 @@ 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 -puN kernel/nsproxy.c~user-ns-implement-user-ns-unshare kernel/nsproxy.c --- a/kernel/nsproxy.c~user-ns-implement-user-ns-unshare +++ a/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 -puN kernel/user_namespace.c~user-ns-implement-user-ns-unshare kernel/user_namespace.c --- a/kernel/user_namespace.c~user-ns-implement-user-ns-unshare +++ a/kernel/user_namespace.c @@ -20,16 +20,86 @@ 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; - int err = 0; + struct user_namespace *new_ns, *old_ns = tsk->nsproxy->user_ns; + int err; if (!old_ns) return 0; get_user_ns(old_ns); + 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 err; } _