From 28c41efd08bf97fc64f75304035ee3943995b68e Mon Sep 17 00:00:00 2001 From: Kirill Tkhai Date: Mon, 3 Aug 2020 13:17:00 +0300 Subject: [PATCH] time: Use generic ns_common::count Switch over time namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai Reviewed-by: Kees Cook Acked-by: Christian Brauner Link: https://lore.kernel.org/r/159644982033.604812.9406853013011123238.stgit@localhost.localdomain Signed-off-by: Christian Brauner --- include/linux/time_namespace.h | 9 ++++----- kernel/time/namespace.c | 9 +++------ 2 files changed, 7 insertions(+), 11 deletions(-) diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h index 5b6031385db0..a51ffc089219 100644 --- a/include/linux/time_namespace.h +++ b/include/linux/time_namespace.h @@ -4,7 +4,6 @@ #include -#include #include #include #include @@ -18,7 +17,6 @@ struct timens_offsets { }; struct time_namespace { - struct kref kref; struct user_namespace *user_ns; struct ucounts *ucounts; struct ns_common ns; @@ -37,20 +35,21 @@ extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns); static inline struct time_namespace *get_time_ns(struct time_namespace *ns) { - kref_get(&ns->kref); + refcount_inc(&ns->ns.count); return ns; } struct time_namespace *copy_time_ns(unsigned long flags, struct user_namespace *user_ns, struct time_namespace *old_ns); -void free_time_ns(struct kref *kref); +void free_time_ns(struct time_namespace *ns); int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk); struct vdso_data *arch_get_vdso_data(void *vvar_page); static inline void put_time_ns(struct time_namespace *ns) { - kref_put(&ns->kref, free_time_ns); + if (refcount_dec_and_test(&ns->ns.count)) + free_time_ns(ns); } void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m); diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index afc65e6be33e..c4c829eb3511 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -92,7 +92,7 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns, if (!ns) goto fail_dec; - kref_init(&ns->kref); + refcount_set(&ns->ns.count, 1); ns->vvar_page = alloc_page(GFP_KERNEL | __GFP_ZERO); if (!ns->vvar_page) @@ -226,11 +226,8 @@ out: mutex_unlock(&offset_lock); } -void free_time_ns(struct kref *kref) +void free_time_ns(struct time_namespace *ns) { - struct time_namespace *ns; - - ns = container_of(kref, struct time_namespace, kref); dec_time_namespaces(ns->ucounts); put_user_ns(ns->user_ns); ns_free_inum(&ns->ns); @@ -464,7 +461,7 @@ const struct proc_ns_operations timens_for_children_operations = { }; struct time_namespace init_time_ns = { - .kref = KREF_INIT(3), + .ns.count = REFCOUNT_INIT(3), .user_ns = &init_user_ns, .ns.inum = PROC_TIME_INIT_INO, .ns.ops = &timens_operations, -- 2.20.1