From patchwork Fri Oct 20 08:16:02 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Reshetova, Elena" X-Patchwork-Id: 10019185 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 7CAD960224 for ; Fri, 20 Oct 2017 08:18:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 66D9D28EA7 for ; Fri, 20 Oct 2017 08:18:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5BD2928EC9; Fri, 20 Oct 2017 08:18:24 +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 CEA7828EA7 for ; Fri, 20 Oct 2017 08:18:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752490AbdJTIRI (ORCPT ); Fri, 20 Oct 2017 04:17:08 -0400 Received: from mga07.intel.com ([134.134.136.100]:7859 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752211AbdJTIQb (ORCPT ); Fri, 20 Oct 2017 04:16:31 -0400 Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga105.jf.intel.com with ESMTP; 20 Oct 2017 01:16:31 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,405,1503385200"; d="scan'208";a="325528355" Received: from elena-thinkpad-x230.fi.intel.com ([10.237.72.87]) by fmsmga004.fm.intel.com with ESMTP; 20 Oct 2017 01:16:27 -0700 From: Elena Reshetova To: axboe@kernel.dk Cc: james.bottomley@hansenpartnership.com, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-btrfs@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, fujita.tomonori@lab.ntt.co.jp, mingo@redhat.com, clm@fb.com, jbacik@fb.com, dsterba@suse.com, keescook@chromium.org, Elena Reshetova Subject: [PATCH 6/6] drivers, block: convert xen_blkif.refcnt from atomic_t to refcount_t Date: Fri, 20 Oct 2017 11:16:02 +0300 Message-Id: <1508487362-26663-7-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1508487362-26663-1-git-send-email-elena.reshetova@intel.com> References: <1508487362-26663-1-git-send-email-elena.reshetova@intel.com> Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@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 xen_blkif.refcnt 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 --- drivers/block/xen-blkback/common.h | 7 ++++--- drivers/block/xen-blkback/xenbus.c | 2 +- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index ecb35fe..0c3320d 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -35,6 +35,7 @@ #include #include #include +#include #include #include #include @@ -319,7 +320,7 @@ struct xen_blkif { struct xen_vbd vbd; /* Back pointer to the backend_info. */ struct backend_info *be; - atomic_t refcnt; + refcount_t refcnt; /* for barrier (drain) requests */ struct completion drain_complete; atomic_t drain; @@ -372,10 +373,10 @@ struct pending_req { (_v)->bdev->bd_part->nr_sects : \ get_capacity((_v)->bdev->bd_disk)) -#define xen_blkif_get(_b) (atomic_inc(&(_b)->refcnt)) +#define xen_blkif_get(_b) (refcount_inc(&(_b)->refcnt)) #define xen_blkif_put(_b) \ do { \ - if (atomic_dec_and_test(&(_b)->refcnt)) \ + if (refcount_dec_and_test(&(_b)->refcnt)) \ schedule_work(&(_b)->free_work);\ } while (0) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 21c1be1..5955b61 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -176,7 +176,7 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) return ERR_PTR(-ENOMEM); blkif->domid = domid; - atomic_set(&blkif->refcnt, 1); + refcount_set(&blkif->refcnt, 1); init_completion(&blkif->drain_complete); INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);