Ian Kent <[email protected]> writes: 2> On Thu, 2015-03-19 at 19:47 +0000, Al Viro wrote: >> On Tue, Mar 17, 2015 at 10:45:09AM +0800, Ian Kent wrote: >> > From: Ian Kent <[email protected]> >> > >> > The mnt_namespace definition will be needed by the usermode helper >> > contained execution implementation, move it to include/linux/mount.h. >> >> I really don't like that. AFAICS, the root of the evil is that fscking >> nsproxy keeps a pointer to mnt_namespace while all it really needs to >> know about is the address of ns_common field embedded into it. Let's see... > > Thought that might be the case. > >> >> fs/namespace.c:697: struct mnt_namespace *ns = current->nsproxy->mnt_ns; >> fs/namespace.c:770: return mnt->mnt_ns == current->nsproxy->mnt_ns; >> fs/namespace.c:1502: return ns_capable(current->nsproxy->mnt_ns->user_ns, >> CAP_SYS_ADMIN); >> fs/namespace.c:1587: return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; >> fs/namespace.c:2293: struct user_namespace *user_ns = >> current->nsproxy->mnt_ns->user_ns; >> fs/namespace.c:2961: touch_mnt_namespace(current->nsproxy->mnt_ns); >> fs/namespace.c:3003: init_task.nsproxy->mnt_ns = ns; >> fs/namespace.c:3101: ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; >> fs/namespace.c:3119: struct mnt_namespace *ns = current->nsproxy->mnt_ns; >> fs/namespace.c:3159: ns = &nsproxy->mnt_ns->ns; >> fs/namespace.c:3187: put_mnt_ns(nsproxy->mnt_ns); >> fs/namespace.c:3188: nsproxy->mnt_ns = mnt_ns; >> fs/pnode.c:282: user_ns = current->nsproxy->mnt_ns->user_ns; >> fs/proc_namespace.c:246: if (!nsp || !nsp->mnt_ns) { >> fs/proc_namespace.c:251: ns = nsp->mnt_ns; >> include/linux/nsproxy.h:33: struct mnt_namespace *mnt_ns; >> kernel/nsproxy.c:37: .mnt_ns = NULL, >> kernel/nsproxy.c:70: new_nsp->mnt_ns = copy_mnt_ns(flags, >> tsk->nsproxy->mnt_ns, user_ns, new_fs); >> kernel/nsproxy.c:71: if (IS_ERR(new_nsp->mnt_ns)) { >> kernel/nsproxy.c:72: err = PTR_ERR(new_nsp->mnt_ns); >> kernel/nsproxy.c:113: if (new_nsp->mnt_ns) >> kernel/nsproxy.c:114: put_mnt_ns(new_nsp->mnt_ns); >> kernel/nsproxy.c:160: if (ns->mnt_ns) >> kernel/nsproxy.c:161: put_mnt_ns(ns->mnt_ns); >> >> OK, so we need >> >> a) add in fs/mount.h >> static inline struct mnt_namespace *current_mnt_ns(void) >> { >> return current->nsproxy->mnt_ns; >> } >> >> and replace a lot of open-coded instances. >> >> b) lift to_mnt_ns() into fs/mount.h (as static inline) >> >> c) switch put_mnt_ns() to struct ns_common *, replacing put_mnt_ns(ns) >> with put_mnt_ns(&ns->ns) and using to_mnt_ns() in the body to recover >> the original. >> >> d) make copy_mnt_ns() take and return struct ns_common * (same treatment as >> for >> put_mnt_ns() in (c); replace >> new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, user_ns, >> new_fs); >> if (IS_ERR(new_nsp->mnt_ns)) { >> err = PTR_ERR(new_nsp->mnt_ns); >> goto out_ns; >> } >> with >> ns = copy_mnt_ns(flags, &tsk->nsproxy->mnt_ns->ns, user_ns, new_fs); >> if (IS_ERR(ns)) { >> err = PTR_ERR(ns); >> goto out_ns; >> } >> new_nsp->mnt_ns = to_mnt_ns(ns); >> >> e) replace struct mnt_namespace *mnt_ns with struct ns_common *__mnt_ns in >> nsproxy.h, deal with users of mnt_ns by >> * everywhere in the tree replace put_mnt_ns(&...->mnt_ns->ns) with >> put_mnt_ns(...->__mnt_ns) (i.e. modify the lines modified by (c) again). >> * in fs/namespace.c replace >> init_task.nsproxy->mnt_ns = ns; >> with >> init_task.nsproxy->__mnt_ns = &ns->ns; >> replace >> ns = &nsproxy->mnt_ns->ns; >> with >> ns = nsproxy->__mnt_ns; >> replace >> nsproxy->mnt_ns = mnt_ns; >> with >> nsproxy>__mnt_ns = &mnt_ns->ns; >> * in fs/proc_namespace.c replace >> ns = nsp->mnt_ns; >> with >> ns = to_mnt_ns(nsp->__mnt_ns); >> and >> if (!nsp || !nsp->mnt_ns) { >> with >> if (!nsp || !nsp->__mnt_ns) { >> * in kernel/nsproxy.c: replace >> ns = copy_mnt_ns(flags, &tsk->nsproxy->mnt_ns->ns, user_ns, new_fs); >> added in (d) with >> ns = copy_mnt_ns(flags, tsk->nsproxy->__mnt_ns, user_ns, new_fs); >> and >> new_nsp->mnt_ns = to_mnt_ns(ns); >> with >> new_nsp->__mnt_ns = ns; >> The rest of mnt_ns in that file get replaced by __mnt_ns. >> * in current_mnt_ns() replace ...->mnt_ns with to_mnt_ns(...->__mnt_ns) >> >> Do you want me to push such a series in vfs.git? After such 5 commits we >> have >> no pointers to struct mnt_namespace in nsproxy.h *and* no need for your >> patches >> to dig into ->mnt_ns->ns - we already have that as ->__mnt_ns. > > Yes please, I'd be more confident if you did this than me, there's > already enough to worry about with the series.
Given that this patchset is a security hole waiting to happen I don't see why Al should bother unless there are good reasons to do this otherwise. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
