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=-15.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 CC32EC433E0 for ; Fri, 22 Jan 2021 15:02:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A07B123AC8 for ; Fri, 22 Jan 2021 15:02:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729063AbhAVPCn (ORCPT ); Fri, 22 Jan 2021 10:02:43 -0500 Received: from foss.arm.com ([217.140.110.172]:51792 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728732AbhAVOzL (ORCPT ); Fri, 22 Jan 2021 09:55:11 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CE3ED11D4; Fri, 22 Jan 2021 06:54:23 -0800 (PST) Received: from [10.37.8.28] (unknown [10.37.8.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AEEBA3F66E; Fri, 22 Jan 2021 06:54:21 -0800 (PST) Subject: Re: [PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report() To: Andrey Konovalov Cc: Linux ARM , LKML , kasan-dev , Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Leon Romanovsky , Catalin Marinas , Will Deacon , Mark Rutland , "Paul E . McKenney" , Naresh Kamboju References: <20210122143748.50089-1-vincenzo.frascino@arm.com> <20210122143748.50089-3-vincenzo.frascino@arm.com> From: Vincenzo Frascino Message-ID: Date: Fri, 22 Jan 2021 14:58:12 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/22/21 2:46 PM, Andrey Konovalov wrote: > On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino > wrote: >> >> With the introduction of KASAN_HW_TAGS, kasan_report() dereferences >> the address passed as a parameter. > > It doesn't dereference the address, it accesses the metadata. And only > when addr_has_metadata() succeeds. > Yes, this is correct. Seems I forgot again to unstash something. Will fix it in v4. >> >> Add a comment to make sure that the preconditions to the function are >> explicitly clarified. >> >> Note: An invalid address (e.g. NULL) passed to the function when, >> KASAN_HW_TAGS is enabled, leads to a kernel panic. > > This is no longer true, right? Commit description needs to be updated. > >> >> Cc: Andrey Ryabinin >> Cc: Alexander Potapenko >> Cc: Dmitry Vyukov >> Cc: Leon Romanovsky >> Cc: Andrey Konovalov >> Signed-off-by: Vincenzo Frascino >> --- >> include/linux/kasan.h | 7 +++++++ >> mm/kasan/kasan.h | 2 +- >> 2 files changed, 8 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/kasan.h b/include/linux/kasan.h >> index fe1ae73ff8b5..0aea9e2a2a01 100644 >> --- a/include/linux/kasan.h >> +++ b/include/linux/kasan.h >> @@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr) >> return (void *)arch_kasan_reset_tag(addr); >> } >> >> +/** >> + * kasan_report - print a report about a bad memory access detected by KASAN >> + * @addr: address of the bad access >> + * @size: size of the bad access >> + * @is_write: whether the bad access is a write or a read >> + * @ip: instruction pointer for the accessibility check or the bad access itself >> + */ > > Looks good, thanks! > >> bool kasan_report(unsigned long addr, size_t size, >> bool is_write, unsigned long ip); >> >> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h >> index cc4d9e1d49b1..8c706e7652f2 100644 >> --- a/mm/kasan/kasan.h >> +++ b/mm/kasan/kasan.h >> @@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write, >> >> static inline bool addr_has_metadata(const void *addr) >> { >> - return true; >> + return (is_vmalloc_addr(addr) || virt_addr_valid(addr)); >> } > > Let's put this change into a separate patch. > Ok, it will be done in v4. >> >> #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ >> -- >> 2.30.0 >> -- Regards, Vincenzo