From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752457AbdJTHjA (ORCPT ); Fri, 20 Oct 2017 03:39:00 -0400 Received: from mga01.intel.com ([192.55.52.88]:21160 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752170AbdJTHi5 (ORCPT ); Fri, 20 Oct 2017 03:38:57 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,405,1503385200"; d="scan'208";a="1233064279" From: Elena Reshetova To: dm-devel@redhat.com Cc: linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, kent.overstreet@gmail.com, koverstreet@google.com, ejt@redhat.comg, snitzer@redhat.com, shli@kernel.org, agk@redhat.com, peterz@infradead.org, keescook@chromium.org, Elena Reshetova Subject: [PATCH 3/4] dm: convert dm_dev_internal.count from atomic_t to refcount_t Date: Fri, 20 Oct 2017 10:37:38 +0300 Message-Id: <1508485059-21881-4-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1508485059-21881-1-git-send-email-elena.reshetova@intel.com> References: <1508485059-21881-1-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 dm_dev_internal.count 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/md/dm-table.c | 6 +++--- drivers/md/dm.h | 3 ++- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index ef7b8f2..fc7d240 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -451,15 +451,15 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, return r; } - atomic_set(&dd->count, 0); + refcount_set(&dd->count, 1); list_add(&dd->list, &t->devices); } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) { r = upgrade_mode(dd, mode, t->md); if (r) return r; + refcount_inc(&dd->count); } - atomic_inc(&dd->count); *result = dd->dm_dev; return 0; @@ -515,7 +515,7 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d) dm_device_name(ti->table->md), d->name); return; } - if (atomic_dec_and_test(&dd->count)) { + if (refcount_dec_and_test(&dd->count)) { dm_put_table_device(ti->table->md, d); list_del(&dd->list); kfree(dd); diff --git a/drivers/md/dm.h b/drivers/md/dm.h index 38c84c0..36399bb8 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -19,6 +19,7 @@ #include #include #include +#include #include "dm-stats.h" @@ -38,7 +39,7 @@ */ struct dm_dev_internal { struct list_head list; - atomic_t count; + refcount_t count; struct dm_dev *dm_dev; }; -- 2.7.4