From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753143AbdJTLQ2 (ORCPT ); Fri, 20 Oct 2017 07:16:28 -0400 Received: from mga09.intel.com ([134.134.136.24]:35826 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753090AbdJTLQE (ORCPT ); Fri, 20 Oct 2017 07:16:04 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,405,1503385200"; d="scan'208";a="1208012378" From: Elena Reshetova To: darrick.wong@oracle.com Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, peterz@infradead.org, keescook@chromium.org, Elena Reshetova Subject: [PATCH 4/5] fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to refcount_t Date: Fri, 20 Oct 2017 14:07:57 +0300 Message-Id: <1508497678-10508-5-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1508497678-10508-1-git-send-email-elena.reshetova@intel.com> References: <1508497678-10508-1-git-send-email-elena.reshetova@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 xfs_cui_log_item.cui_refcount 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 --- fs/xfs/xfs_refcount_item.c | 6 +++--- fs/xfs/xfs_refcount_item.h | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/xfs/xfs_refcount_item.c b/fs/xfs/xfs_refcount_item.c index 8f2e2fa..004d002 100644 --- a/fs/xfs/xfs_refcount_item.c +++ b/fs/xfs/xfs_refcount_item.c @@ -205,7 +205,7 @@ xfs_cui_init( cuip->cui_format.cui_nextents = nextents; cuip->cui_format.cui_id = (uintptr_t)(void *)cuip; atomic_set(&cuip->cui_next_extent, 0); - atomic_set(&cuip->cui_refcount, 2); + refcount_set(&cuip->cui_refcount, 2); return cuip; } @@ -221,8 +221,8 @@ void xfs_cui_release( struct xfs_cui_log_item *cuip) { - ASSERT(atomic_read(&cuip->cui_refcount) > 0); - if (atomic_dec_and_test(&cuip->cui_refcount)) { + ASSERT(refcount_read(&cuip->cui_refcount) > 0); + if (refcount_dec_and_test(&cuip->cui_refcount)) { xfs_trans_ail_remove(&cuip->cui_item, SHUTDOWN_LOG_IO_ERROR); xfs_cui_item_free(cuip); } diff --git a/fs/xfs/xfs_refcount_item.h b/fs/xfs/xfs_refcount_item.h index 5b74ddd..abc0377 100644 --- a/fs/xfs/xfs_refcount_item.h +++ b/fs/xfs/xfs_refcount_item.h @@ -63,7 +63,7 @@ struct kmem_zone; */ struct xfs_cui_log_item { struct xfs_log_item cui_item; - atomic_t cui_refcount; + refcount_t cui_refcount; atomic_t cui_next_extent; unsigned long cui_flags; /* misc flags */ struct xfs_cui_log_format cui_format; -- 2.7.4