Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751814AbdH3MX6 (ORCPT ); Wed, 30 Aug 2017 08:23:58 -0400 Received: from mga06.intel.com ([134.134.136.31]:21550 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751788AbdH3MXz (ORCPT ); Wed, 30 Aug 2017 08:23:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,448,1498546800"; d="scan'208";a="895512204" From: Elena Reshetova To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, tj@kernel.org, mingo@redhat.com, hannes@cmpxchg.org, lizefan@huawei.com, acme@kernel.org, alexander.shishkin@linux.intel.com, eparis@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, luto@kernel.org, keescook@chromium.org, tglx@linutronix.de, dvhart@infradead.org, ebiederm@xmission.com, Elena Reshetova Subject: [PATCH 11/15] nsproxy: convert nsproxy.count to refcount_t Date: Wed, 30 Aug 2017 15:22:49 +0300 Message-Id: <1504095773-22895-12-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1504095773-22895-1-git-send-email-elena.reshetova@intel.com> References: <1504095773-22895-1-git-send-email-elena.reshetova@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2685 Lines: 89 atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable nsproxy.count is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova --- include/linux/nsproxy.h | 6 +++--- kernel/nsproxy.c | 6 +++--- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h index ac0d65b..f862ba8 100644 --- a/include/linux/nsproxy.h +++ b/include/linux/nsproxy.h @@ -28,7 +28,7 @@ struct fs_struct; * nsproxy is copied. */ struct nsproxy { - atomic_t count; + refcount_t count; struct uts_namespace *uts_ns; struct ipc_namespace *ipc_ns; struct mnt_namespace *mnt_ns; @@ -74,14 +74,14 @@ int __init nsproxy_cache_init(void); static inline void put_nsproxy(struct nsproxy *ns) { - if (atomic_dec_and_test(&ns->count)) { + if (refcount_dec_and_test(&ns->count)) { free_nsproxy(ns); } } static inline void get_nsproxy(struct nsproxy *ns) { - atomic_inc(&ns->count); + refcount_inc(&ns->count); } #endif diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c index f6c5d33..5bfe691 100644 --- a/kernel/nsproxy.c +++ b/kernel/nsproxy.c @@ -31,7 +31,7 @@ static struct kmem_cache *nsproxy_cachep; struct nsproxy init_nsproxy = { - .count = ATOMIC_INIT(1), + .count = REFCOUNT_INIT(1), .uts_ns = &init_uts_ns, #if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC) .ipc_ns = &init_ipc_ns, @@ -52,7 +52,7 @@ static inline struct nsproxy *create_nsproxy(void) nsproxy = kmem_cache_alloc(nsproxy_cachep, GFP_KERNEL); if (nsproxy) - atomic_set(&nsproxy->count, 1); + refcount_set(&nsproxy->count, 1); return nsproxy; } @@ -225,7 +225,7 @@ void switch_task_namespaces(struct task_struct *p, struct nsproxy *new) p->nsproxy = new; task_unlock(p); - if (ns && atomic_dec_and_test(&ns->count)) + if (ns && refcount_dec_and_test(&ns->count)) free_nsproxy(ns); } -- 2.7.4