From patchwork Fri Oct 20 11:07:55 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Reshetova, Elena" X-Patchwork-Id: 10019871 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 0AB0A60234 for ; Fri, 20 Oct 2017 11:16:50 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F34B428EAA for ; Fri, 20 Oct 2017 11:16:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E805428EB0; Fri, 20 Oct 2017 11:16:49 +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 6E33128EAA for ; Fri, 20 Oct 2017 11:16:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753061AbdJTLQB (ORCPT ); Fri, 20 Oct 2017 07:16:01 -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 S1753052AbdJTLP7 (ORCPT ); Fri, 20 Oct 2017 07:15:59 -0400 Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Oct 2017 04:15:59 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,405,1503385200"; d="scan'208";a="1208012318" Received: from elena-thinkpad-x230.fi.intel.com ([10.237.72.87]) by fmsmga001.fm.intel.com with ESMTP; 20 Oct 2017 04:15:57 -0700 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 2/5] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Date: Fri, 20 Oct 2017 14:07:55 +0300 Message-Id: <1508497678-10508-3-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-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@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 xfs_efi_log_item.efi_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_extfree_item.c | 6 +++--- fs/xfs/xfs_extfree_item.h | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c index 44f8c54..dfe2bcb 100644 --- a/fs/xfs/xfs_extfree_item.c +++ b/fs/xfs/xfs_extfree_item.c @@ -220,7 +220,7 @@ xfs_efi_init( efip->efi_format.efi_nextents = nextents; efip->efi_format.efi_id = (uintptr_t)(void *)efip; atomic_set(&efip->efi_next_extent, 0); - atomic_set(&efip->efi_refcount, 2); + refcount_set(&efip->efi_refcount, 2); return efip; } @@ -290,8 +290,8 @@ void xfs_efi_release( struct xfs_efi_log_item *efip) { - ASSERT(atomic_read(&efip->efi_refcount) > 0); - if (atomic_dec_and_test(&efip->efi_refcount)) { + ASSERT(refcount_read(&efip->efi_refcount) > 0); + if (refcount_dec_and_test(&efip->efi_refcount)) { xfs_trans_ail_remove(&efip->efi_item, SHUTDOWN_LOG_IO_ERROR); xfs_efi_item_free(efip); } diff --git a/fs/xfs/xfs_extfree_item.h b/fs/xfs/xfs_extfree_item.h index a32c794..fadf736 100644 --- a/fs/xfs/xfs_extfree_item.h +++ b/fs/xfs/xfs_extfree_item.h @@ -64,7 +64,7 @@ struct kmem_zone; */ typedef struct xfs_efi_log_item { xfs_log_item_t efi_item; - atomic_t efi_refcount; + refcount_t efi_refcount; atomic_t efi_next_extent; unsigned long efi_flags; /* misc flags */ xfs_efi_log_format_t efi_format;