From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f69.google.com (mail-io1-f69.google.com [209.85.166.69]) by kanga.kvack.org (Postfix) with ESMTP id DB7008E0001 for ; Wed, 12 Sep 2018 12:34:18 -0400 (EDT) Received: by mail-io1-f69.google.com with SMTP id x5-v6so955339ioa.6 for ; Wed, 12 Sep 2018 09:34:18 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id s20-v6sor880345jan.144.2018.09.12.09.34.17 for (Google Transport Security); Wed, 12 Sep 2018 09:34:17 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <19d757c2cafc277f0143a8ac34e179061f3487f5.1535462971.git.andreyknvl@google.com> References: <19d757c2cafc277f0143a8ac34e179061f3487f5.1535462971.git.andreyknvl@google.com> From: Dmitry Vyukov Date: Wed, 12 Sep 2018 18:33:56 +0200 Message-ID: Subject: Re: [PATCH v6 06/18] khwasan, arm64: untag virt address in __kimg_to_phys and _virt_addr_is_linear Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Konovalov Cc: Andrey Ryabinin , Alexander Potapenko , Catalin Marinas , Will Deacon , Christoph Lameter , Andrew Morton , Mark Rutland , Nick Desaulniers , Marc Zyngier , Dave Martin , Ard Biesheuvel , "Eric W . Biederman" , Ingo Molnar , Paul Lawrence , Geert Uytterhoeven , Arnd Bergmann , "Kirill A . Shutemov" , Greg Kroah-Hartman , Kate Stewart , Mike Rapoport , kasan-dev , linux-doc@vger.kernel.org, LKML , Linux ARM , linux-sparse@vger.kernel.org, Linux-MM , "open list:KERNEL BUILD + fi..." , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Jann Horn , Mark Brand , Chintan Pandya , Vishwath Mohan On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov wrote: > __kimg_to_phys (which is used by virt_to_phys) and _virt_addr_is_linear > (which is used by virt_addr_valid) assume that the top byte of the address > is 0xff, which isn't always the case with KHWASAN enabled. > > The solution is to reset the tag in those macros. > > Signed-off-by: Andrey Konovalov > --- > arch/arm64/include/asm/memory.h | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > index f5e262ee76c1..f5e2953b7009 100644 > --- a/arch/arm64/include/asm/memory.h > +++ b/arch/arm64/include/asm/memory.h > @@ -92,6 +92,13 @@ > #define KASAN_THREAD_SHIFT 0 > #endif > > +#ifdef CONFIG_KASAN_HW > +#define KASAN_TAG_SHIFTED(tag) ((unsigned long)(tag) << 56) > +#define KASAN_SET_TAG(addr, tag) (((addr) & ~KASAN_TAG_SHIFTED(0xff)) | \ > + KASAN_TAG_SHIFTED(tag)) > +#define KASAN_RESET_TAG(addr) KASAN_SET_TAG(addr, 0xff) > +#endif > + Wouldn't it be better to #define KASAN_RESET_TAG(addr) addr when CONFIG_KASAN_HW is not enabled, and then not duplicate the macros below? That's what we do in kasan.h for all hooks. I see that a subsequent patch duplicates yet another macro in this file. While we could use: #define __kimg_to_phys(addr) (KASAN_RESET_TAG(addr) - kimage_voffset) with and without kasan. Duplicating them increases risk that somebody will change only the non-kasan version but forget kasan version. > #define MIN_THREAD_SHIFT (14 + KASAN_THREAD_SHIFT) > > /* > @@ -232,7 +239,12 @@ static inline unsigned long kaslr_offset(void) > #define __is_lm_address(addr) (!!((addr) & BIT(VA_BITS - 1))) > > #define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET) > + > +#ifdef CONFIG_KASAN_HW > +#define __kimg_to_phys(addr) (KASAN_RESET_TAG(addr) - kimage_voffset) > +#else > #define __kimg_to_phys(addr) ((addr) - kimage_voffset) > +#endif > > #define __virt_to_phys_nodebug(x) ({ \ > phys_addr_t __x = (phys_addr_t)(x); \ > @@ -308,7 +320,13 @@ static inline void *phys_to_virt(phys_addr_t x) > #endif > #endif > > +#ifdef CONFIG_KASAN_HW > +#define _virt_addr_is_linear(kaddr) (KASAN_RESET_TAG((u64)(kaddr)) >= \ > + PAGE_OFFSET) > +#else > #define _virt_addr_is_linear(kaddr) (((u64)(kaddr)) >= PAGE_OFFSET) > +#endif > + > #define virt_addr_valid(kaddr) (_virt_addr_is_linear(kaddr) && \ > _virt_addr_valid(kaddr)) > > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog >