From f2a8d52e0a4db968c346c4332630a71cba377567 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Tue, 5 May 2020 16:04:30 +0200 Subject: [PATCH] nsproxy: add struct nsset 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 switches the existing setns logic over without causing a change in setns() behavior. This brings setns() closer to how unshare() works(). The prepare_ns() function is responsible to prepare all necessary information. This has two reasons. First it minimizes dependencies between individual namespaces, i.e. all install handler can expect that all fields are properly initialized independent in what order they are called in. Second, this makes the code easier to maintain and easier to follow if it needs to be changed. The prepare_ns() helper will only be switched over to use a flags argument in the next patch. Here it will still use nstype as a simple integer argument which was argued would be clearer. I'm not particularly opinionated about this if it really helps or not. The struct nsset itself already contains the flags field since its name already indicates that it can contain information required by different namespaces. None of this should have functional consequences. Signed-off-by: Christian Brauner Reviewed-by: Serge Hallyn Cc: Eric W. Biederman Cc: Serge Hallyn Cc: Jann Horn Cc: Michael Kerrisk Cc: Aleksa Sarai Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com --- fs/namespace.c | 10 ++-- include/linux/mnt_namespace.h | 1 + include/linux/nsproxy.h | 24 ++++++++++ include/linux/proc_ns.h | 4 +- ipc/namespace.c | 7 ++- kernel/cgroup/namespace.c | 5 +- kernel/nsproxy.c | 90 ++++++++++++++++++++++++++++++----- kernel/pid_namespace.c | 5 +- kernel/time/namespace.c | 5 +- kernel/user_namespace.c | 8 ++-- kernel/utsname.c | 5 +- net/core/net_namespace.c | 5 +- 12 files changed, 132 insertions(+), 37 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index a28e4db075ede2..62899fad4a0404 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3954,16 +3954,18 @@ 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)) + !ns_capable(user_ns, CAP_SYS_CHROOT) || + !ns_capable(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 35942084cd40d5..007cfa52efb230 100644 --- a/include/linux/mnt_namespace.h +++ b/include/linux/mnt_namespace.h @@ -6,6 +6,7 @@ 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 *); diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h index 074f395b9ad254..cdb171efc7cb05 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 6abe85c346813a..75807ecef880f1 100644 --- a/include/linux/proc_ns.h +++ b/include/linux/proc_ns.h @@ -8,7 +8,7 @@ #include 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 b3ca1476ca5118..fdc3b5f3f53aa7 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)) + !ns_capable(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 b05f1dd58a6220..812a61afd538a1 100644 --- a/kernel/cgroup/namespace.c +++ b/kernel/cgroup/namespace.c @@ -95,11 +95,12 @@ 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) || + if (!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN) || !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c index ed9882108cd28f..b7954fd6047538 100644 --- a/kernel/nsproxy.c +++ b/kernel/nsproxy.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -257,12 +258,79 @@ 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(int nstype, 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 (nstype == CLONE_NEWUSER) + nsset->cred = prepare_creds(); + else + nsset->cred = current_cred(); + if (!nsset->cred) + goto out; + + if (nstype == CLONE_NEWNS) + nsset->fs = me->fs; + + nsset->flags = nstype; + 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; +} + 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 +342,16 @@ 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(ns->ops->type, &nsset); + if (err) goto out; - } - err = ns->ops->install(new_nsproxy, ns); - if (err) { - free_nsproxy(new_nsproxy); - goto out; + err = ns->ops->install(&nsset, ns); + if (!err) { + commit_nsset(&nsset); + perf_event_namespaces(current); } - 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 01f8ba32cc0c7f..11db2bdbb41e56 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)) + !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; /* diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index 53bce347cd50bc..5d9fc22d836a08 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -280,8 +280,9 @@ 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; @@ -289,7 +290,7 @@ static int timens_install(struct nsproxy *nsproxy, struct ns_common *new) return -EUSERS; if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || - !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + !ns_capable(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 8eadadc478f9aa..87804e0371fe19 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 f0e4911930092f..e488d0e2ab457b 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)) + !ns_capable(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 190ca66a383b78..dcd61aca343eca 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)) + !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; put_net(nsproxy->net_ns);