From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754027AbcHAPAc (ORCPT ); Mon, 1 Aug 2016 11:00:32 -0400 Received: from mail-wm0-f50.google.com ([74.125.82.50]:36407 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752595AbcHAPAM (ORCPT ); Mon, 1 Aug 2016 11:00:12 -0400 From: Alexander Potapenko To: dvyukov@google.com, kcc@google.com, aryabinin@virtuozzo.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 Subject: [PATCH] kasan: avoid overflowing quarantine size on low memory systems Date: Mon, 1 Aug 2016 16:59:23 +0200 Message-Id: <1470063563-96266-1-git-send-email-glider@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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", + ); + new_quarantine_size = 0; + } else { + new_quarantine_size -= percpu_quarantines; + } WRITE_ONCE(quarantine_size, new_quarantine_size); last = global_quarantine.head; -- 2.8.0.rc3.226.g39d4020