From 9a56493f6942c0e2df1579986128721da96e00d8 Mon Sep 17 00:00:00 2001 From: Kirill Tkhai Date: Mon, 3 Aug 2020 13:16:21 +0300 Subject: [PATCH] uts: Use generic ns_common::count Switch over uts 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/159644978167.604812.1773586504374412107.stgit@localhost.localdomain Signed-off-by: Christian Brauner --- include/linux/utsname.h | 9 ++++----- init/version.c | 2 +- kernel/utsname.c | 7 ++----- 3 files changed, 7 insertions(+), 11 deletions(-) diff --git a/include/linux/utsname.h b/include/linux/utsname.h index 44429d9142ca..2b1737c9b244 100644 --- a/include/linux/utsname.h +++ b/include/linux/utsname.h @@ -4,7 +4,6 @@ #include -#include #include #include #include @@ -22,7 +21,6 @@ struct user_namespace; extern struct user_namespace init_user_ns; struct uts_namespace { - struct kref kref; struct new_utsname name; struct user_namespace *user_ns; struct ucounts *ucounts; @@ -33,16 +31,17 @@ extern struct uts_namespace init_uts_ns; #ifdef CONFIG_UTS_NS static inline void get_uts_ns(struct uts_namespace *ns) { - kref_get(&ns->kref); + refcount_inc(&ns->ns.count); } extern struct uts_namespace *copy_utsname(unsigned long flags, struct user_namespace *user_ns, struct uts_namespace *old_ns); -extern void free_uts_ns(struct kref *kref); +extern void free_uts_ns(struct uts_namespace *ns); static inline void put_uts_ns(struct uts_namespace *ns) { - kref_put(&ns->kref, free_uts_ns); + if (refcount_dec_and_test(&ns->ns.count)) + free_uts_ns(ns); } void uts_ns_init(void); diff --git a/init/version.c b/init/version.c index cba341161b58..80d2b7566b39 100644 --- a/init/version.c +++ b/init/version.c @@ -25,7 +25,7 @@ int version_string(LINUX_VERSION_CODE); #endif struct uts_namespace init_uts_ns = { - .kref = KREF_INIT(2), + .ns.count = REFCOUNT_INIT(2), .name = { .sysname = UTS_SYSNAME, .nodename = UTS_NODENAME, diff --git a/kernel/utsname.c b/kernel/utsname.c index e488d0e2ab45..b1ac3ca870f2 100644 --- a/kernel/utsname.c +++ b/kernel/utsname.c @@ -33,7 +33,7 @@ static struct uts_namespace *create_uts_ns(void) uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL); if (uts_ns) - kref_init(&uts_ns->kref); + refcount_set(&uts_ns->ns.count, 1); return uts_ns; } @@ -103,11 +103,8 @@ struct uts_namespace *copy_utsname(unsigned long flags, return new_ns; } -void free_uts_ns(struct kref *kref) +void free_uts_ns(struct uts_namespace *ns) { - struct uts_namespace *ns; - - ns = container_of(kref, struct uts_namespace, kref); dec_uts_namespaces(ns->ucounts); put_user_ns(ns->user_ns); ns_free_inum(&ns->ns);