From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755147AbcHAUl7 (ORCPT ); Mon, 1 Aug 2016 16:41:59 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:41298 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755089AbcHAUlt (ORCPT ); Mon, 1 Aug 2016 16:41:49 -0400 Date: Mon, 1 Aug 2016 13:30:10 -0700 From: Andrew Morton To: Alexander Potapenko Cc: dvyukov@google.com, kcc@google.com, aryabinin@virtuozzo.com, adech.fo@gmail.com, cl@linux.com, rostedt@goodmis.org, js1304@gmail.com, iamjoonsoo.kim@lge.com, kuthonuzo.luruo@hpe.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] kasan: avoid overflowing quarantine size on low memory systems Message-Id: <20160801133010.08b1733dc7f62fe68713c0ba@linux-foundation.org> In-Reply-To: <1470063563-96266-1-git-send-email-glider@google.com> References: <1470063563-96266-1-git-send-email-glider@google.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 1 Aug 2016 16:59:23 +0200 Alexander Potapenko wrote: > If the total amount of memory assigned to quarantine is less than the > amount of memory assigned to per-cpu quarantines, |new_quarantine_size| > may overflow. Instead, set it to zero. > > --- a/mm/kasan/quarantine.c > +++ b/mm/kasan/quarantine.c > @@ -214,7 +214,15 @@ void quarantine_reduce(void) > */ > new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) / > QUARANTINE_FRACTION; > - new_quarantine_size -= QUARANTINE_PERCPU_SIZE * num_online_cpus(); > + percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); > + if (new_quarantine_size < percpu_quarantines) { > + WARN_ONCE(1, > + "Too little memory, disabling global KASAN quarantine.\n", > + ); > + new_quarantine_size = 0; > + } else { > + new_quarantine_size -= percpu_quarantines; > + } > WRITE_ONCE(quarantine_size, new_quarantine_size); > > last = global_quarantine.head; This is a little tidier: --- a/mm/kasan/quarantine.c~kasan-avoid-overflowing-quarantine-size-on-low-memory-systems-fix +++ a/mm/kasan/quarantine.c @@ -217,14 +217,11 @@ void quarantine_reduce(void) new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) / QUARANTINE_FRACTION; percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); - if (new_quarantine_size < percpu_quarantines) { - WARN_ONCE(1, - "Too little memory, disabling global KASAN quarantine.\n", - ); + if (WARN_ONCE(new_quarantine_size < percpu_quarantines, + "Too little memory, disabling global KASAN quarantine.\n")) new_quarantine_size = 0; - } else { + else new_quarantine_size -= percpu_quarantines; - } WRITE_ONCE(quarantine_size, new_quarantine_size); last = global_quarantine.head; _