From patchwork Fri Aug 25 09:41:20 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Reshetova, Elena" X-Patchwork-Id: 9921615 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B8CCB60349 for ; Fri, 25 Aug 2017 09:46:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id ABF482625B for ; Fri, 25 Aug 2017 09:46:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A0AEF27D4A; Fri, 25 Aug 2017 09:46:18 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5047D2625B for ; Fri, 25 Aug 2017 09:46:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755669AbdHYJlz (ORCPT ); Fri, 25 Aug 2017 05:41:55 -0400 Received: from mga04.intel.com ([192.55.52.120]:13015 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755428AbdHYJlx (ORCPT ); Fri, 25 Aug 2017 05:41:53 -0400 Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Aug 2017 02:41:53 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,424,1498546800"; d="scan'208";a="893999660" Received: from elena-thinkpad-x230.fi.intel.com ([10.237.72.88]) by FMSMGA003.fm.intel.com with ESMTP; 25 Aug 2017 02:41:48 -0700 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 03/15] sched: convert user_struct.__count to refcount_t Date: Fri, 25 Aug 2017 12:41:20 +0300 Message-Id: <1503654092-15471-4-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1503654092-15471-1-git-send-email-elena.reshetova@intel.com> References: <1503654092-15471-1-git-send-email-elena.reshetova@intel.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 user_struct.__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/sched/user.h | 5 +++-- kernel/user.c | 8 ++++---- 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/include/linux/sched/user.h b/include/linux/sched/user.h index 3c07e41..afcbf19 100644 --- a/include/linux/sched/user.h +++ b/include/linux/sched/user.h @@ -3,6 +3,7 @@ #include #include +#include struct key; @@ -10,7 +11,7 @@ struct key; * Some day this will be a full-fledged user tracking system.. */ struct user_struct { - atomic_t __count; /* reference count */ + refcount_t __count; /* reference count */ atomic_t processes; /* How many processes does this user have? */ atomic_t sigpending; /* How many pending signals does this user have? */ #ifdef CONFIG_FANOTIFY @@ -54,7 +55,7 @@ extern struct user_struct root_user; extern struct user_struct * alloc_uid(kuid_t); static inline struct user_struct *get_uid(struct user_struct *u) { - atomic_inc(&u->__count); + refcount_inc(&u->__count); return u; } extern void free_uid(struct user_struct *); diff --git a/kernel/user.c b/kernel/user.c index 00281ad..c072348 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -90,7 +90,7 @@ static DEFINE_SPINLOCK(uidhash_lock); /* root_user.__count is 1, for init task cred */ struct user_struct root_user = { - .__count = ATOMIC_INIT(1), + .__count = REFCOUNT_INIT(1), .processes = ATOMIC_INIT(1), .sigpending = ATOMIC_INIT(0), .locked_shm = 0, @@ -116,7 +116,7 @@ static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent) hlist_for_each_entry(user, hashent, uidhash_node) { if (uid_eq(user->uid, uid)) { - atomic_inc(&user->__count); + refcount_inc(&user->__count); return user; } } @@ -163,7 +163,7 @@ void free_uid(struct user_struct *up) return; local_irq_save(flags); - if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) + if (refcount_dec_and_lock(&up->__count, &uidhash_lock)) free_user(up, flags); else local_irq_restore(flags); @@ -184,7 +184,7 @@ struct user_struct *alloc_uid(kuid_t uid) goto out_unlock; new->uid = uid; - atomic_set(&new->__count, 1); + refcount_set(&new->__count, 1); /* * Before adding this, check whether we raced