From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757943AbdJKTTZ (ORCPT ); Wed, 11 Oct 2017 15:19:25 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:38288 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757851AbdJKTTY (ORCPT ); Wed, 11 Oct 2017 15:19:24 -0400 X-Google-Smtp-Source: AOwi7QAOJWuvQoeWw84Oerf2WDZo2glYP/O7af1lG+W/ndjdBLkMMC+ZrWz3Tj2Jty7VXGte2eezLA== Subject: Re: [PATCH 10/11] Change mapping of kasan_zero_page int readonly To: Abbott Liu , linux@armlinux.org.uk, aryabinin@virtuozzo.com, afzal.mohd.ma@gmail.com, labbott@redhat.com, kirill.shutemov@linux.intel.com, mhocko@suse.com, cdall@linaro.org, marc.zyngier@arm.com, catalin.marinas@arm.com, akpm@linux-foundation.org, mawilcox@microsoft.com, tglx@linutronix.de, thgarnie@google.com, keescook@chromium.org, arnd@arndb.de, vladimir.murzin@arm.com, tixy@linaro.org, ard.biesheuvel@linaro.org, robin.murphy@arm.com, mingo@kernel.org, grygorii.strashko@linaro.org Cc: glider@google.com, dvyukov@google.com, opendmb@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, jiazhenghua@huawei.com, dylix.dailei@huawei.com, zengweilin@huawei.com, heshaoliang@huawei.com References: <20171011082227.20546-1-liuwenliang@huawei.com> <20171011082227.20546-11-liuwenliang@huawei.com> From: Florian Fainelli Message-ID: Date: Wed, 11 Oct 2017 12:19:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20171011082227.20546-11-liuwenliang@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/11/2017 01:22 AM, Abbott Liu wrote: > Because the kasan_zero_page(which is used as the shadow > region for some memory that KASan doesn't need to track.) won't be writen > after kasan_init, so change the mapping of kasan_zero_page into readonly. > > Cc: Andrey Ryabinin > --- > arch/arm/mm/kasan_init.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c > index 7cfdc39..c11826a 100644 > --- a/arch/arm/mm/kasan_init.c > +++ b/arch/arm/mm/kasan_init.c > @@ -200,6 +200,7 @@ void __init kasan_init(void) > { > struct memblock_region *reg; > u64 orig_ttbr0; > + int i; Nit: unsigned int i. > > orig_ttbr0 = cpu_get_ttbr(0); > > @@ -243,6 +244,17 @@ void __init kasan_init(void) > create_mapping((unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR), > (unsigned long)kasan_mem_to_shadow((void *)(PKMAP_BASE+PMD_SIZE)), > NUMA_NO_NODE); > + > + /* > + * KAsan may reuse the contents of kasan_zero_pte directly, so we > + * should make sure that it maps the zero page read-only. > + */ > + for (i = 0; i < PTRS_PER_PTE; i++) > + set_pte_at(&init_mm, KASAN_SHADOW_START + i*PAGE_SIZE, > + &kasan_zero_pte[i], pfn_pte( > + virt_to_pfn(kasan_zero_page), > + __pgprot(_L_PTE_DEFAULT | L_PTE_DIRTY | L_PTE_XN | L_PTE_RDONLY))); > + memset(kasan_zero_page, 0, PAGE_SIZE); > cpu_set_ttbr0(orig_ttbr0); > flush_cache_all(); > local_flush_bp_all(); > -- Florian