From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-f199.google.com (mail-lj1-f199.google.com [209.85.208.199]) by kanga.kvack.org (Postfix) with ESMTP id D2ED18E0002 for ; Tue, 15 Jan 2019 12:24:59 -0500 (EST) Received: by mail-lj1-f199.google.com with SMTP id t22-v6so909213lji.14 for ; Tue, 15 Jan 2019 09:24:59 -0800 (PST) Received: from relay.sw.ru (relay.sw.ru. [185.231.240.75]) by mx.google.com with ESMTPS id m25-v6si3096358ljb.153.2019.01.15.09.24.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Jan 2019 09:24:58 -0800 (PST) Subject: Re: [PATCH v2] page_poison: play nicely with KASAN References: <2e46c139-70d3-dc86-28c9-a9f263651b57@virtuozzo.com> <20190114233405.67843-1-cai@lca.pw> From: Andrey Ryabinin Message-ID: <3a2aefb4-f108-5354-ddb9-7a35d8e0b3f2@virtuozzo.com> Date: Tue, 15 Jan 2019 20:25:20 +0300 MIME-Version: 1.0 In-Reply-To: <20190114233405.67843-1-cai@lca.pw> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Qian Cai , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org On 1/15/19 2:34 AM, Qian Cai wrote: > KASAN does not play well with the page poisoning > (CONFIG_PAGE_POISONING). It triggers false positives in the allocation > path, > > BUG: KASAN: use-after-free in memchr_inv+0x2ea/0x330 > Read of size 8 at addr ffff88881f800000 by task swapper/0 > CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc1+ #54 > Call Trace: > dump_stack+0xe0/0x19a > print_address_description.cold.2+0x9/0x28b > kasan_report.cold.3+0x7a/0xb5 > __asan_report_load8_noabort+0x19/0x20 > memchr_inv+0x2ea/0x330 > kernel_poison_pages+0x103/0x3d5 > get_page_from_freelist+0x15e7/0x4d90 > > because KASAN has not yet unpoisoned the shadow page for allocation > before it checks memchr_inv() but only found a stale poison pattern. > > Also, false positives in free path, > > BUG: KASAN: slab-out-of-bounds in kernel_poison_pages+0x29e/0x3d5 > Write of size 4096 at addr ffff8888112cc000 by task swapper/0/1 > CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc1+ #55 > Call Trace: > dump_stack+0xe0/0x19a > print_address_description.cold.2+0x9/0x28b > kasan_report.cold.3+0x7a/0xb5 > check_memory_region+0x22d/0x250 > memset+0x28/0x40 > kernel_poison_pages+0x29e/0x3d5 > __free_pages_ok+0x75f/0x13e0 > > due to KASAN adds poisoned redzones around slab objects, but the page > poisoning needs to poison the whole page. > > Signed-off-by: Qian Cai > --- > Acked-by: Andrey Ryabinin