From patchwork Fri Oct 20 08:16:01 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Reshetova, Elena" X-Patchwork-Id: 10019169 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 6A60760224 for ; Fri, 20 Oct 2017 08:16:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5B55128EA7 for ; Fri, 20 Oct 2017 08:16:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4FA3E28EC9; Fri, 20 Oct 2017 08:16:58 +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 0403828EA7 for ; Fri, 20 Oct 2017 08:16:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752493AbdJTIQd (ORCPT ); Fri, 20 Oct 2017 04:16:33 -0400 Received: from mga07.intel.com ([134.134.136.100]:7859 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752272AbdJTIQ2 (ORCPT ); Fri, 20 Oct 2017 04:16:28 -0400 Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga105.jf.intel.com with ESMTP; 20 Oct 2017 01:16:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,405,1503385200"; d="scan'208";a="325528344" Received: from elena-thinkpad-x230.fi.intel.com ([10.237.72.87]) by fmsmga004.fm.intel.com with ESMTP; 20 Oct 2017 01:16:23 -0700 From: Elena Reshetova To: axboe@kernel.dk Cc: james.bottomley@hansenpartnership.com, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-btrfs@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, fujita.tomonori@lab.ntt.co.jp, mingo@redhat.com, clm@fb.com, jbacik@fb.com, dsterba@suse.com, keescook@chromium.org, Elena Reshetova Subject: [PATCH 5/6] block: convert bsg_device.ref_count from atomic_t to refcount_t Date: Fri, 20 Oct 2017 11:16:01 +0300 Message-Id: <1508487362-26663-6-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1508487362-26663-1-git-send-email-elena.reshetova@intel.com> References: <1508487362-26663-1-git-send-email-elena.reshetova@intel.com> Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@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 bsg_device.ref_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 --- block/bsg.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/bsg.c b/block/bsg.c index ee1335c..6c98422 100644 --- a/block/bsg.c +++ b/block/bsg.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include @@ -38,7 +39,7 @@ struct bsg_device { struct list_head busy_list; struct list_head done_list; struct hlist_node dev_list; - atomic_t ref_count; + refcount_t ref_count; int queued_cmds; int done_cmds; wait_queue_head_t wq_done; @@ -710,7 +711,7 @@ static int bsg_put_device(struct bsg_device *bd) mutex_lock(&bsg_mutex); - do_free = atomic_dec_and_test(&bd->ref_count); + do_free = refcount_dec_and_test(&bd->ref_count); if (!do_free) { mutex_unlock(&bsg_mutex); goto out; @@ -768,7 +769,7 @@ static struct bsg_device *bsg_add_device(struct inode *inode, bsg_set_block(bd, file); - atomic_set(&bd->ref_count, 1); + refcount_set(&bd->ref_count, 1); mutex_lock(&bsg_mutex); hlist_add_head(&bd->dev_list, bsg_dev_idx_hash(iminor(inode))); @@ -788,7 +789,7 @@ static struct bsg_device *__bsg_get_device(int minor, struct request_queue *q) hlist_for_each_entry(bd, bsg_dev_idx_hash(minor), dev_list) { if (bd->queue == q) { - atomic_inc(&bd->ref_count); + refcount_inc(&bd->ref_count); goto found; } }