From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752834AbcHJWuS (ORCPT ); Wed, 10 Aug 2016 18:50:18 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:54477 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752342AbcHJWuQ (ORCPT ); Wed, 10 Aug 2016 18:50:16 -0400 Date: Wed, 10 Aug 2016 15:50:15 -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 v2] kasan: avoid overflowing quarantine size on low memory systems Message-Id: <20160810155015.bffc044a171466b2fdf5195e@linux-foundation.org> In-Reply-To: <1470133620-28683-1-git-send-email-glider@google.com> References: <1470133620-28683-1-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 Tue, 2 Aug 2016 12:27:00 +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 > @@ -196,7 +196,7 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache) > > void quarantine_reduce(void) > { > - size_t new_quarantine_size; > + size_t new_quarantine_size, percpu_quarantines; > unsigned long flags; > struct qlist_head to_free = QLIST_INIT; > size_t size_to_free = 0; > @@ -214,7 +214,9 @@ 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(); > + new_quarantine_size = (new_quarantine_size < percpu_quarantines) ? > + 0 : new_quarantine_size - percpu_quarantines; > WRITE_ONCE(quarantine_size, new_quarantine_size); > > last = global_quarantine.head; Confused. Which kernel version is this supposed to apply to?