From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) by kanga.kvack.org (Postfix) with ESMTP id CE7538E0002 for ; Mon, 14 Jan 2019 18:34:20 -0500 (EST) Received: by mail-qk1-f198.google.com with SMTP id c84so745668qkb.13 for ; Mon, 14 Jan 2019 15:34:20 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id e5sor34632502qkj.13.2019.01.14.15.34.19 for (Google Transport Security); Mon, 14 Jan 2019 15:34:19 -0800 (PST) From: Qian Cai Subject: [PATCH v2] page_poison: play nicely with KASAN Date: Mon, 14 Jan 2019 18:34:05 -0500 Message-Id: <20190114233405.67843-1-cai@lca.pw> In-Reply-To: <2e46c139-70d3-dc86-28c9-a9f263651b57@virtuozzo.com> References: <2e46c139-70d3-dc86-28c9-a9f263651b57@virtuozzo.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: aryabinin@virtuozzo.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai 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 --- v2: use kasan_disable/enable_current() instead. mm/page_alloc.c | 2 +- mm/page_poison.c | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d295c9bc01a8..906250a9b89c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1945,8 +1945,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order, arch_alloc_page(page, order); kernel_map_pages(page, 1 << order, 1); - kernel_poison_pages(page, 1 << order, 1); kasan_alloc_pages(page, order); + kernel_poison_pages(page, 1 << order, 1); set_page_owner(page, order, gfp_flags); } diff --git a/mm/page_poison.c b/mm/page_poison.c index f0c15e9017c0..21d4f97cb49b 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -6,6 +6,7 @@ #include #include #include +#include static bool want_page_poisoning __read_mostly; @@ -40,7 +41,10 @@ static void poison_page(struct page *page) { void *addr = kmap_atomic(page); + /* KASAN still think the page is in-use, so skip it. */ + kasan_disable_current(); memset(addr, PAGE_POISON, PAGE_SIZE); + kasan_enable_current(); kunmap_atomic(addr); } -- 2.17.2 (Apple Git-113)