From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43905C433E0 for ; Wed, 13 Jan 2021 16:55:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DCF7523383 for ; Wed, 13 Jan 2021 16:55:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727691AbhAMQz2 (ORCPT ); Wed, 13 Jan 2021 11:55:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:49828 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726661AbhAMQz2 (ORCPT ); Wed, 13 Jan 2021 11:55:28 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7DC072339D; Wed, 13 Jan 2021 16:54:44 +0000 (UTC) Date: Wed, 13 Jan 2021 16:54:41 +0000 From: Catalin Marinas To: Andrey Konovalov Cc: Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Marco Elver , Andrew Morton , Will Deacon , Andrey Ryabinin , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] kasan, arm64: fix pointer tags in KASAN reports Message-ID: <20210113165441.GC27045@gaia> References: <1965508bcbec62699715d32bef91628ef55b4b44.1610553774.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1965508bcbec62699715d32bef91628ef55b4b44.1610553774.git.andreyknvl@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 13, 2021 at 05:03:30PM +0100, Andrey Konovalov wrote: > As of the "arm64: expose FAR_EL1 tag bits in siginfo" patch, the address > that is passed to report_tag_fault has pointer tags in the format of 0x0X, > while KASAN uses 0xFX format (note the difference in the top 4 bits). > > Fix up the pointer tag before calling kasan_report. > > Link: https://linux-review.googlesource.com/id/I9ced973866036d8679e8f4ae325de547eb969649 > Fixes: dceec3ff7807 ("arm64: expose FAR_EL1 tag bits in siginfo") > Fixes: 4291e9ee6189 ("kasan, arm64: print report from tag fault handler") > Signed-off-by: Andrey Konovalov > --- > arch/arm64/mm/fault.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 3c40da479899..a218f6f2fdc8 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -304,6 +304,8 @@ static void report_tag_fault(unsigned long addr, unsigned int esr, > { > bool is_write = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0; > > + /* The format of KASAN tags is 0xF. */ > + addr |= (0xF0UL << MTE_TAG_SHIFT); Ah, I see, that top 4 bits are zeroed by do_tag_check_fault(). When this was added, the only tag faults were generated for user addresses. Anyway, I'd rather fix it in there based on bit 55, something like (only compile-tested): diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 3c40da479899..2b71079d2d32 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -709,10 +709,11 @@ static int do_tag_check_fault(unsigned long far, unsigned int esr, struct pt_regs *regs) { /* - * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN for tag - * check faults. Mask them out now so that userspace doesn't see them. + * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN + * for tag check faults. Set them to the corresponding bits in the + * untagged address. */ - far &= (1UL << 60) - 1; + far = (untagged_addr(far) & ~MTE_TAG_MASK) | (far & MTE_TAG_MASK) ; do_bad_area(far, esr, regs); return 0; } -- Catalin