From patchwork Fri Aug 25 09:41:19 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Reshetova, Elena" X-Patchwork-Id: 9921555 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 65ADF6022E for ; Fri, 25 Aug 2017 09:42:07 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5A4A927F88 for ; Fri, 25 Aug 2017 09:42:07 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4BDDE27F97; Fri, 25 Aug 2017 09:42:07 +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=ham 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 A548627F88 for ; Fri, 25 Aug 2017 09:42:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755475AbdHYJlv (ORCPT ); Fri, 25 Aug 2017 05:41:51 -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 S1755648AbdHYJls (ORCPT ); Fri, 25 Aug 2017 05:41:48 -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 02:41:48 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,424,1498546800"; d="scan'208";a="893999641" Received: from elena-thinkpad-x230.fi.intel.com ([10.237.72.88]) by FMSMGA003.fm.intel.com with ESMTP; 25 Aug 2017 02:41:44 -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 02/15] sched: convert signal_struct.sigcnt to refcount_t Date: Fri, 25 Aug 2017 12:41:19 +0300 Message-Id: <1503654092-15471-3-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 signal_struct.sigcnt 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/signal.h | 2 +- kernel/fork.c | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 4d5cdf1..c5f1a67 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -77,7 +77,7 @@ struct thread_group_cputimer { * the locking of signal_struct. */ struct signal_struct { - atomic_t sigcnt; + refcount_t sigcnt; atomic_t live; int nr_threads; struct list_head thread_head; diff --git a/kernel/fork.c b/kernel/fork.c index 43bcd20..d2e2eb0 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -400,7 +400,7 @@ static inline void free_signal_struct(struct signal_struct *sig) static inline void put_signal_struct(struct signal_struct *sig) { - if (atomic_dec_and_test(&sig->sigcnt)) + if (refcount_dec_and_test(&sig->sigcnt)) free_signal_struct(sig); } @@ -1382,7 +1382,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) sig->nr_threads = 1; atomic_set(&sig->live, 1); - atomic_set(&sig->sigcnt, 1); + refcount_set(&sig->sigcnt, 1); /* list_add(thread_node, thread_head) without INIT_LIST_HEAD() */ sig->thread_head = (struct list_head)LIST_HEAD_INIT(tsk->thread_node); @@ -1887,7 +1887,7 @@ static __latent_entropy struct task_struct *copy_process( } else { current->signal->nr_threads++; atomic_inc(¤t->signal->live); - atomic_inc(¤t->signal->sigcnt); + refcount_inc(¤t->signal->sigcnt); list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); list_add_tail_rcu(&p->thread_node,