From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id 649326B0005 for ; Tue, 2 Aug 2016 05:58:58 -0400 (EDT) Received: by mail-io0-f198.google.com with SMTP id n69so364500358ion.0 for ; Tue, 02 Aug 2016 02:58:58 -0700 (PDT) Received: from EUR03-AM5-obe.outbound.protection.outlook.com (mail-eopbgr30133.outbound.protection.outlook.com. [40.107.3.133]) by mx.google.com with ESMTPS id w9si844950oie.126.2016.08.02.02.58.57 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 02 Aug 2016 02:58:57 -0700 (PDT) Subject: Re: [PATCH] kasan: avoid overflowing quarantine size on low memory systems References: <1470063563-96266-1-git-send-email-glider@google.com> From: Andrey Ryabinin Message-ID: <57A06F23.9080804@virtuozzo.com> Date: Tue, 2 Aug 2016 13:00:03 +0300 MIME-Version: 1.0 In-Reply-To: <1470063563-96266-1-git-send-email-glider@google.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Alexander Potapenko , dvyukov@google.com, kcc@google.com, adech.fo@gmail.com, cl@linux.com, akpm@linux-foundation.org, rostedt@goodmis.org, js1304@gmail.com, iamjoonsoo.kim@lge.com, kuthonuzo.luruo@hpe.com Cc: kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 08/01/2016 05:59 PM, 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. > Just curious, how did find this? Overflow is possible if system has more than 32 cpus per GB of memory. AFIAK this quite unusual. > Reported-by: Dmitry Vyukov > Fixes: 55834c59098d ("mm: kasan: initial memory quarantine > implementation") > Signed-off-by: Alexander Potapenko > --- > mm/kasan/quarantine.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c > index 65793f1..416d3b0 100644 > --- 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 +214,15 @@ 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", > + ); Why WARN? I'd suggest pr_warn_once(); > + new_quarantine_size = 0; > + } else { > + new_quarantine_size -= percpu_quarantines; > + } > WRITE_ONCE(quarantine_size, new_quarantine_size); > > last = global_quarantine.head; > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org