Add a simple struct nsset. It holds all necessary pieces to switch to a new set of namespaces without leaving a task in a half-switched state which we will make use of in the next patch. This patch simply switches the existing setns logic over without causing a change in setns() behavior. This brings setns() closer to how unshare() works().
Cc: Eric W. Biederman <[email protected]> Cc: Serge Hallyn <[email protected]> Signed-off-by: Christian Brauner <[email protected]> --- /* v2 */ patch introduced --- fs/namespace.c | 17 +++++-- include/linux/mnt_namespace.h | 2 + include/linux/nsproxy.h | 24 +++++++++ include/linux/proc_ns.h | 4 +- ipc/namespace.c | 9 ++-- kernel/cgroup/namespace.c | 7 +-- kernel/nsproxy.c | 94 ++++++++++++++++++++++++++++++----- kernel/pid_namespace.c | 7 +-- kernel/time/namespace.c | 7 +-- kernel/user_namespace.c | 8 +-- kernel/utsname.c | 7 +-- net/core/net_namespace.c | 7 +-- 12 files changed, 150 insertions(+), 43 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index a28e4db075ed..91d2b86aadfb 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1733,6 +1733,11 @@ static struct mnt_namespace *to_mnt_ns(struct ns_common *ns) return container_of(ns, struct mnt_namespace, ns); } +struct ns_common *mnt_ns_to_common(struct mnt_namespace *mnt) +{ + return &mnt->ns; +} + static bool mnt_ns_loop(struct dentry *dentry) { /* Could bind mounting the mount namespace inode cause a @@ -3954,16 +3959,18 @@ static void mntns_put(struct ns_common *ns) put_mnt_ns(to_mnt_ns(ns)); } -static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns) +static int mntns_install(struct nsset *nsset, struct ns_common *ns) { - struct fs_struct *fs = current->fs; + struct nsproxy *nsproxy = nsset->nsproxy; + struct fs_struct *fs = nsset->fs; struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; + struct user_namespace *user_ns = nsset->cred->user_ns; struct path root; int err; - if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || - !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || - !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + if (!ns_capable_cred(nsset->cred, mnt_ns->user_ns, CAP_SYS_ADMIN) || + !ns_capable_cred(nsset->cred, user_ns, CAP_SYS_CHROOT) || + !ns_capable_cred(nsset->cred, user_ns, CAP_SYS_ADMIN)) return -EPERM; if (is_anon_ns(mnt_ns)) diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h index 35942084cd40..664dd3b06f34 100644 --- a/include/linux/mnt_namespace.h +++ b/include/linux/mnt_namespace.h @@ -6,10 +6,12 @@ struct mnt_namespace; struct fs_struct; struct user_namespace; +struct ns_common; extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *, struct user_namespace *, struct fs_struct *); extern void put_mnt_ns(struct mnt_namespace *ns); +extern struct ns_common *mnt_ns_to_common(struct mnt_namespace *); extern const struct file_operations proc_mounts_operations; extern const struct file_operations proc_mountinfo_operations; diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h index 074f395b9ad2..cdb171efc7cb 100644 --- a/include/linux/nsproxy.h +++ b/include/linux/nsproxy.h @@ -41,6 +41,30 @@ struct nsproxy { }; extern struct nsproxy init_nsproxy; +/* + * A structure to encompass all bits needed to install + * a partial or complete new set of namespaces. + * + * If a new user namespace is requested cred will + * point to a modifiable set of credentials. If a pointer + * to a modifiable set is needed nsset_cred() must be + * used and tested. + */ +struct nsset { + unsigned flags; + struct nsproxy *nsproxy; + struct fs_struct *fs; + const struct cred *cred; +}; + +static inline struct cred *nsset_cred(struct nsset *set) +{ + if (set->flags & CLONE_NEWUSER) + return (struct cred *)set->cred; + + return NULL; +} + /* * the namespaces access rules are: * diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h index 6abe85c34681..75807ecef880 100644 --- a/include/linux/proc_ns.h +++ b/include/linux/proc_ns.h @@ -8,7 +8,7 @@ #include <linux/ns_common.h> struct pid_namespace; -struct nsproxy; +struct nsset; struct path; struct task_struct; struct inode; @@ -19,7 +19,7 @@ struct proc_ns_operations { int type; struct ns_common *(*get)(struct task_struct *task); void (*put)(struct ns_common *ns); - int (*install)(struct nsproxy *nsproxy, struct ns_common *ns); + int (*install)(struct nsset *nsset, struct ns_common *ns); struct user_namespace *(*owner)(struct ns_common *ns); struct ns_common *(*get_parent)(struct ns_common *ns); } __randomize_layout; diff --git a/ipc/namespace.c b/ipc/namespace.c index b3ca1476ca51..df6aa2deab18 100644 --- a/ipc/namespace.c +++ b/ipc/namespace.c @@ -177,15 +177,14 @@ static void ipcns_put(struct ns_common *ns) return put_ipc_ns(to_ipc_ns(ns)); } -static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new) +static int ipcns_install(struct nsset *nsset, struct ns_common *new) { + struct nsproxy *nsproxy = nsset->nsproxy; struct ipc_namespace *ns = to_ipc_ns(new); - if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || - !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + if (!ns_capable_cred(nsset->cred, ns->user_ns, CAP_SYS_ADMIN) || + !ns_capable_cred(nsset->cred, nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; - /* Ditch state from the old ipc namespace */ - exit_sem(current); put_ipc_ns(nsproxy->ipc_ns); nsproxy->ipc_ns = get_ipc_ns(ns); return 0; diff --git a/kernel/cgroup/namespace.c b/kernel/cgroup/namespace.c index b05f1dd58a62..01279c9e6dee 100644 --- a/kernel/cgroup/namespace.c +++ b/kernel/cgroup/namespace.c @@ -95,12 +95,13 @@ static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns) return container_of(ns, struct cgroup_namespace, ns); } -static int cgroupns_install(struct nsproxy *nsproxy, struct ns_common *ns) +static int cgroupns_install(struct nsset *nsset, struct ns_common *ns) { + struct nsproxy *nsproxy = nsset->nsproxy; struct cgroup_namespace *cgroup_ns = to_cg_ns(ns); - if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN) || - !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN)) + if (!ns_capable_cred(nsset->cred, nsset->cred->user_ns, CAP_SYS_ADMIN) || + !ns_capable_cred(nsset->cred, cgroup_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; /* Don't need to do anything if we are attaching to our own cgroupns. */ diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c index ed9882108cd2..2da463bab58a 100644 --- a/kernel/nsproxy.c +++ b/kernel/nsproxy.c @@ -19,6 +19,7 @@ #include <net/net_namespace.h> #include <linux/ipc_namespace.h> #include <linux/time_namespace.h> +#include <linux/fs_struct.h> #include <linux/proc_ns.h> #include <linux/file.h> #include <linux/syscalls.h> @@ -257,12 +258,85 @@ void exit_task_namespaces(struct task_struct *p) switch_task_namespaces(p, NULL); } +static void put_nsset(struct nsset *nsset) +{ + unsigned flags = nsset->flags; + + if (flags & CLONE_NEWUSER) + put_cred(nsset_cred(nsset)); + if (nsset->nsproxy) + free_nsproxy(nsset->nsproxy); +} + +static int prepare_nsset(unsigned flags, struct nsset *nsset) +{ + struct task_struct *me = current; + + nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs); + if (IS_ERR(nsset->nsproxy)) + return PTR_ERR(nsset->nsproxy); + + if (flags & CLONE_NEWUSER) + nsset->cred = prepare_creds(); + else + nsset->cred = current_cred(); + if (!nsset->cred) + goto out; + + if (flags & CLONE_NEWNS) + nsset->fs = me->fs; + + nsset->flags = flags; + return 0; + +out: + put_nsset(nsset); + return -ENOMEM; +} + +/* + * This is the point of no return. There are just a few namespaces + * that do some actual work here and it's sufficiently minimal that + * a separate ns_common operation seems unnecessary for now. + * Unshare is doing the same thing. If we'll end up needing to do + * more in a given namespace or a helper here is ultimately not + * exported anymore a simple commit handler for each namespace + * should be added to ns_common. + */ +static void commit_nsset(struct nsset *nsset) +{ + unsigned flags = nsset->flags; + struct task_struct *me = current; + +#ifdef CONFIG_USER_NS + if (flags & CLONE_NEWUSER) { + /* transfer ownership */ + commit_creds(nsset_cred(nsset)); + nsset->cred = NULL; + } +#endif + +#ifdef CONFIG_IPC_NS + if (flags & CLONE_NEWIPC) + exit_sem(me); +#endif + + /* transfer ownership */ + switch_task_namespaces(me, nsset->nsproxy); + nsset->nsproxy = NULL; +} + +static inline int validate_ns(struct nsset *nsset, struct ns_common *ns) +{ + return ns->ops->install(nsset, ns); +} + SYSCALL_DEFINE2(setns, int, fd, int, nstype) { struct task_struct *tsk = current; - struct nsproxy *new_nsproxy; struct file *file; struct ns_common *ns; + struct nsset nsset = {}; int err; file = proc_ns_fget(fd); @@ -274,20 +348,16 @@ SYSCALL_DEFINE2(setns, int, fd, int, nstype) if (nstype && (ns->ops->type != nstype)) goto out; - new_nsproxy = create_new_namespaces(0, tsk, current_user_ns(), tsk->fs); - if (IS_ERR(new_nsproxy)) { - err = PTR_ERR(new_nsproxy); + err = prepare_nsset(nstype, &nsset); + if (err) goto out; - } - err = ns->ops->install(new_nsproxy, ns); - if (err) { - free_nsproxy(new_nsproxy); - goto out; + err = validate_ns(&nsset, ns); + if (!err) { + commit_nsset(&nsset); + perf_event_namespaces(tsk); } - switch_task_namespaces(tsk, new_nsproxy); - - perf_event_namespaces(tsk); + put_nsset(&nsset); out: fput(file); return err; diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index 01f8ba32cc0c..b0b0e1055812 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -378,13 +378,14 @@ static void pidns_put(struct ns_common *ns) put_pid_ns(to_pid_ns(ns)); } -static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns) +static int pidns_install(struct nsset *nsset, struct ns_common *ns) { + struct nsproxy *nsproxy = nsset->nsproxy; struct pid_namespace *active = task_active_pid_ns(current); struct pid_namespace *ancestor, *new = to_pid_ns(ns); - if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) || - !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + if (!ns_capable_cred(nsset->cred, new->user_ns, CAP_SYS_ADMIN) || + !ns_capable_cred(nsset->cred, nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; /* diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index 53bce347cd50..8ff16ef947ef 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -280,16 +280,17 @@ static void timens_put(struct ns_common *ns) put_time_ns(to_time_ns(ns)); } -static int timens_install(struct nsproxy *nsproxy, struct ns_common *new) +static int timens_install(struct nsset *nsset, struct ns_common *new) { + struct nsproxy *nsproxy = nsset->nsproxy; struct time_namespace *ns = to_time_ns(new); int err; if (!current_is_single_threaded()) return -EUSERS; - if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || - !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + if (!ns_capable_cred(nsset->cred, ns->user_ns, CAP_SYS_ADMIN) || + !ns_capable_cred(nsset->cred, nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; timens_set_vvar_page(current, ns); diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 8eadadc478f9..87804e0371fe 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -1253,7 +1253,7 @@ static void userns_put(struct ns_common *ns) put_user_ns(to_user_ns(ns)); } -static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns) +static int userns_install(struct nsset *nsset, struct ns_common *ns) { struct user_namespace *user_ns = to_user_ns(ns); struct cred *cred; @@ -1274,14 +1274,14 @@ static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns) if (!ns_capable(user_ns, CAP_SYS_ADMIN)) return -EPERM; - cred = prepare_creds(); + cred = nsset_cred(nsset); if (!cred) - return -ENOMEM; + return -EINVAL; put_user_ns(cred->user_ns); set_cred_user_ns(cred, get_user_ns(user_ns)); - return commit_creds(cred); + return 0; } struct ns_common *ns_get_owner(struct ns_common *ns) diff --git a/kernel/utsname.c b/kernel/utsname.c index f0e491193009..f8fa76756022 100644 --- a/kernel/utsname.c +++ b/kernel/utsname.c @@ -140,12 +140,13 @@ static void utsns_put(struct ns_common *ns) put_uts_ns(to_uts_ns(ns)); } -static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new) +static int utsns_install(struct nsset *nsset, struct ns_common *new) { + struct nsproxy *nsproxy = nsset->nsproxy; struct uts_namespace *ns = to_uts_ns(new); - if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || - !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + if (!ns_capable_cred(nsset->cred, ns->user_ns, CAP_SYS_ADMIN) || + !ns_capable_cred(nsset->cred, nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; get_uts_ns(ns); diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index 190ca66a383b..e312a5f411ae 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -1353,12 +1353,13 @@ static void netns_put(struct ns_common *ns) put_net(to_net_ns(ns)); } -static int netns_install(struct nsproxy *nsproxy, struct ns_common *ns) +static int netns_install(struct nsset *nsset, struct ns_common *ns) { + struct nsproxy *nsproxy = nsset->nsproxy; struct net *net = to_net_ns(ns); - if (!ns_capable(net->user_ns, CAP_SYS_ADMIN) || - !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + if (!ns_capable_cred(nsset->cred, net->user_ns, CAP_SYS_ADMIN) || + !ns_capable_cred(nsset->cred, nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; put_net(nsproxy->net_ns); -- 2.26.2
