From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752573AbdJTHkL (ORCPT ); Fri, 20 Oct 2017 03:40:11 -0400 Received: from mga01.intel.com ([192.55.52.88]:44912 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752264AbdJTHim (ORCPT ); Fri, 20 Oct 2017 03:38:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,405,1503385200"; d="scan'208";a="1233064269" 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 1/4] bcache: convert cached_dev.count from atomic_t to refcount_t Date: Fri, 20 Oct 2017 10:37:36 +0300 Message-Id: <1508485059-21881-2-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 cached_dev.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/bcache/bcache.h | 7 ++++--- drivers/md/bcache/super.c | 6 +++--- drivers/md/bcache/writeback.h | 2 +- 3 files changed, 8 insertions(+), 7 deletions(-) diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 2ed9bd2..8ed8ad6 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -184,6 +184,7 @@ #include #include #include +#include #include #include @@ -299,7 +300,7 @@ struct cached_dev { struct semaphore sb_write_mutex; /* Refcount on the cache set. Always nonzero when we're caching. */ - atomic_t count; + refcount_t count; struct work_struct detach; /* @@ -806,13 +807,13 @@ do { \ static inline void cached_dev_put(struct cached_dev *dc) { - if (atomic_dec_and_test(&dc->count)) + if (refcount_dec_and_test(&dc->count)) schedule_work(&dc->detach); } static inline bool cached_dev_get(struct cached_dev *dc) { - if (!atomic_inc_not_zero(&dc->count)) + if (!refcount_inc_not_zero(&dc->count)) return false; /* Paired with the mb in cached_dev_attach */ diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index fc0a31b..676e6f4 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -889,7 +889,7 @@ static void cached_dev_detach_finish(struct work_struct *w) closure_init_stack(&cl); BUG_ON(!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)); - BUG_ON(atomic_read(&dc->count)); + BUG_ON(refcount_read(&dc->count)); mutex_lock(&bch_register_lock); @@ -1016,7 +1016,7 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c) * dc->c must be set before dc->count != 0 - paired with the mb in * cached_dev_get() */ - atomic_set(&dc->count, 1); + refcount_set(&dc->count, 1); /* Block writeback thread, but spawn it */ down_write(&dc->writeback_lock); @@ -1028,7 +1028,7 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c) if (BDEV_STATE(&dc->sb) == BDEV_STATE_DIRTY) { bch_sectors_dirty_init(&dc->disk); atomic_set(&dc->has_dirty, 1); - atomic_inc(&dc->count); + refcount_inc(&dc->count); bch_writeback_queue(dc); } diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h index e35421d..5937e0d 100644 --- a/drivers/md/bcache/writeback.h +++ b/drivers/md/bcache/writeback.h @@ -89,7 +89,7 @@ static inline void bch_writeback_add(struct cached_dev *dc) { if (!atomic_read(&dc->has_dirty) && !atomic_xchg(&dc->has_dirty, 1)) { - atomic_inc(&dc->count); + refcount_inc(&dc->count); if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) { SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY); -- 2.7.4