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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 26029C43142 for ; Tue, 19 Jan 2021 18:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F244022AAA for ; Tue, 19 Jan 2021 18:29:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387584AbhASR7Z (ORCPT ); Tue, 19 Jan 2021 12:59:25 -0500 Received: from foss.arm.com ([217.140.110.172]:35076 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726134AbhASPCo (ORCPT ); Tue, 19 Jan 2021 10:02:44 -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 5911DD6E; Tue, 19 Jan 2021 07:01:58 -0800 (PST) Received: from [10.37.8.29] (unknown [10.37.8.29]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 409AF3F66E; Tue, 19 Jan 2021 07:01:56 -0800 (PST) Subject: Re: [PATCH v4 3/5] kasan: Add report for async mode To: Mark Rutland Cc: Catalin Marinas , Andrey Konovalov , Branislav Rankov , Marco Elver , Evgenii Stepanov , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Alexander Potapenko , linux-arm-kernel@lists.infradead.org, Andrey Ryabinin , Will Deacon , Dmitry Vyukov References: <20210118183033.41764-1-vincenzo.frascino@arm.com> <20210118183033.41764-4-vincenzo.frascino@arm.com> <20210119130440.GC17369@gaia> <813f907f-0de8-6b96-c67a-af9aecf31a70@arm.com> <20210119144625.GB2338@C02TD0UTHF1T.local> From: Vincenzo Frascino Message-ID: Date: Tue, 19 Jan 2021 15:05:45 +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: <20210119144625.GB2338@C02TD0UTHF1T.local> 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 1/19/21 2:46 PM, Mark Rutland wrote: > On Tue, Jan 19, 2021 at 02:23:03PM +0000, Vincenzo Frascino wrote: >> On 1/19/21 1:04 PM, Catalin Marinas wrote: >>> On Mon, Jan 18, 2021 at 06:30:31PM +0000, Vincenzo Frascino wrote: > >>>> +bool kasan_report_async(unsigned long addr, size_t size, >>>> + bool is_write, unsigned long ip); >>> >>> We have no address, no size and no is_write information. Do we have a >>> reason to pass all these arguments here? Not sure what SPARC ADI does >>> but they may not have all this information either. We can pass ip as the >>> point where we checked the TFSR reg but that's about it. >> >> I kept the interface generic for future development and mainly to start a >> discussion. I do not have a strong opinion either way. If Andrey agrees as well >> I am happy to change it to what you are suggesting in v5. > > For now, I think it's preferable that this only has parameters that we > can actually provide. That way it's clearer what's going on in both > callers and callees, and we can always rework the prototype later or add > separate variants of the function that can take additional parameters. > > I don't think we even need to use __kasan_report() -- more on that > below. > > [...] > >>>> @@ -388,11 +388,11 @@ static void __kasan_report(unsigned long addr, size_t size, bool is_write, >>>> start_report(&flags); >>>> >>>> print_error_description(&info); >>>> - if (addr_has_metadata(untagged_addr)) >>>> + if (addr_has_metadata(untagged_addr) && (untagged_addr != 0)) >>>> print_tags(get_tag(tagged_addr), info.first_bad_addr); >>>> pr_err("\n"); >>>> >>>> - if (addr_has_metadata(untagged_addr)) { >>>> + if (addr_has_metadata(untagged_addr) && (untagged_addr != 0)) { >>>> print_address_description(untagged_addr, get_tag(tagged_addr)); >>>> pr_err("\n"); >>>> print_memory_metadata(info.first_bad_addr); >>>> @@ -419,6 +419,18 @@ bool kasan_report(unsigned long addr, size_t size, bool is_write, >>>> return ret; >>>> } >>>> >>>> +bool kasan_report_async(unsigned long addr, size_t size, >>>> + bool is_write, unsigned long ip) >>>> +{ >>>> + pr_info("==================================================================\n"); >>>> + pr_info("KASAN: set in asynchronous mode\n"); >>>> + pr_info("KASAN: some information might not be accurate\n"); >>>> + pr_info("KASAN: fault address is ignored\n"); >>>> + pr_info("KASAN: write/read distinction is ignored\n"); >>>> + >>>> + return kasan_report(addr, size, is_write, ip); >>> >>> So just call kasan_report (0, 0, 0, ip) here. > > Given there's no information available, I think it's simpler and > preferable to handle the logging separately, as is done for > kasan_report_invalid_free(). For example, we could do something roughly > like: > > void kasan_report_async(void) > { > unsigned long flags; > > start_report(&flags); > pr_err("BUG: KASAN: Tag mismatch detected asynchronously\n"); > pr_err("KASAN: no fault information available\n"); > dump_stack(); > end_report(&flags); > } > > ... which is easier to consume, since there's no misleading output, > avoids complicating the synchronous reporting path, and we could > consider adding information that's only of use for debugging > asynchronous faults here. > > Since the callside is logged in the backtrace, we don't even need the > synthetic IP parameter. > Agree, especially because I tend to not like to rely on compiler builtins and what you proposed solves the problem ;) I will refactor my code once Andrey had a chance to take a look as well. > Thanks, > Mark. > -- Regards, Vincenzo