From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 S1752793AbdJTLP5 (ORCPT ); Fri, 20 Oct 2017 07:15:57 -0400 From: Elena Reshetova Subject: [PATCH 1/5] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t Date: Fri, 20 Oct 2017 14:07:54 +0300 Message-Id: <1508497678-10508-2-git-send-email-elena.reshetova@intel.com> 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 List-ID: List-Id: xfs To: darrick.wong@oracle.com Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, peterz@infradead.org, keescook@chromium.org, Elena Reshetova 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_bui_log_item.bui_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_bmap_item.c | 6 +++--- fs/xfs/xfs_bmap_item.h | 2 +- fs/xfs/xfs_linux.h | 1 + 3 files changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c index dd136f7..0f2e3d8 100644 --- a/fs/xfs/xfs_bmap_item.c +++ b/fs/xfs/xfs_bmap_item.c @@ -201,7 +201,7 @@ xfs_bui_init( buip->bui_format.bui_nextents = XFS_BUI_MAX_FAST_EXTENTS; buip->bui_format.bui_id = (uintptr_t)(void *)buip; atomic_set(&buip->bui_next_extent, 0); - atomic_set(&buip->bui_refcount, 2); + refcount_set(&buip->bui_refcount, 2); return buip; } @@ -217,8 +217,8 @@ void xfs_bui_release( struct xfs_bui_log_item *buip) { - ASSERT(atomic_read(&buip->bui_refcount) > 0); - if (atomic_dec_and_test(&buip->bui_refcount)) { + ASSERT(refcount_read(&buip->bui_refcount) > 0); + if (refcount_dec_and_test(&buip->bui_refcount)) { xfs_trans_ail_remove(&buip->bui_item, SHUTDOWN_LOG_IO_ERROR); xfs_bui_item_free(buip); } diff --git a/fs/xfs/xfs_bmap_item.h b/fs/xfs/xfs_bmap_item.h index c867daa..7048b14 100644 --- a/fs/xfs/xfs_bmap_item.h +++ b/fs/xfs/xfs_bmap_item.h @@ -61,7 +61,7 @@ struct kmem_zone; */ struct xfs_bui_log_item { struct xfs_log_item bui_item; - atomic_t bui_refcount; + refcount_t bui_refcount; atomic_t bui_next_extent; unsigned long bui_flags; /* misc flags */ struct xfs_bui_log_format bui_format; diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h index dcd1292..0def85f 100644 --- a/fs/xfs/xfs_linux.h +++ b/fs/xfs/xfs_linux.h @@ -20,6 +20,7 @@ #include #include +#include /* * Kernel specific type declarations for XFS -- 2.7.4