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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=ham 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 203BAC433E0 for ; Wed, 13 Jan 2021 16:28:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 96EE823370 for ; Wed, 13 Jan 2021 16:28:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96EE823370 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EB66A6B0160; Wed, 13 Jan 2021 11:28:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E673B6B0162; Wed, 13 Jan 2021 11:28:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D7BD36B0163; Wed, 13 Jan 2021 11:28:53 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0194.hostedemail.com [216.40.44.194]) by kanga.kvack.org (Postfix) with ESMTP id C0BD96B0160 for ; Wed, 13 Jan 2021 11:28:53 -0500 (EST) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 760E3181AEF30 for ; Wed, 13 Jan 2021 16:28:53 +0000 (UTC) X-FDA: 77701285746.26.legs93_2f0df612751f Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id 4726D18070EF9 for ; Wed, 13 Jan 2021 16:28:53 +0000 (UTC) X-HE-Tag: legs93_2f0df612751f X-Filterd-Recvd-Size: 7140 Received: from mail-oi1-f176.google.com (mail-oi1-f176.google.com [209.85.167.176]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Wed, 13 Jan 2021 16:28:52 +0000 (UTC) Received: by mail-oi1-f176.google.com with SMTP id l200so2694693oig.9 for ; Wed, 13 Jan 2021 08:28:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dtGuPSqxThBxFFND3TAs3eyezmIFF8iGuQhEPWlxFw4=; b=sI9xRXQ7bmuA7TJRkjDPjXW3Ct3TrbkRYINplcqCriT13wqmazifZhtY86WTBfwKH7 Qnm3ZuZ0BSgVgVCCqgqYeq5LKetbMAelGxJtIjxrFWGYmLPmnLOion0np3ee7rcJWKsy 4HzkMR3p38leCj5/TqSUAJG6Qtt9DoOsCjLD4eI5M0hLzMJ9lEYnS7yeXxbI2Rr2k7IL 2RDBQPzCtb+RV/q9vvIDtJQhBzyBrpJ5lQuZEsnrM39dRv4np8it98qsVfldq3tIIZ0T fGKih1JACcHtcIaockL+Q1Zuma3IuY9KxJJeJnM+Cd9Qc4Tr5H9Vz7wbbcJtP0yzvDdB R28w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dtGuPSqxThBxFFND3TAs3eyezmIFF8iGuQhEPWlxFw4=; b=Vu2MkTvyAWmaP70Y3WcwluAgAo7pNGIccn/B70EzEiDaSJmAGDDZZlyVl7hWIrqWGq yyjqqLDNC6PplkOfMyzAWHY30R65+xIS20RV6cYIIhoTyAEhBMeCRLG5Qf1MZfaN4R0W O1xrGCs3lb8RSjAPWZ55jZORI9xhx1TTZmwUUP+wUhdZDZ3gVYDgMMWdRuoGY86xPA6Y 2raqFnFY0I6guNeUT5fr4HvWq0KpzTX1sl3+lhshv4AcT2krGK0ef2I0lrAf0njSigGe YB5+vO2y8OaW2JO7GdhTZJ6cjgSvtWXqsXeYJaI6FyA0cxlLmkM59sldfgOHRaPnUBYa jKGA== X-Gm-Message-State: AOAM532DGnG2EGsYQIGBAToLTkTQ5oup3CNlF1MAB9yrrUUT/SNcBN5g nhTY2vWO3T1f8WcmD92ov2V9sfe7oTT8xxcekNNFSA== X-Google-Smtp-Source: ABdhPJwjAqoLrcLjVn73P0G0ScKT22CiHCZFlltMrKpWnEEY7dhsvs+jpP4CxMAsDdiNDcHys/8s8d1eZAiLWUF0MBg= X-Received: by 2002:aca:58d6:: with SMTP id m205mr23481oib.121.1610555331853; Wed, 13 Jan 2021 08:28:51 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Marco Elver Date: Wed, 13 Jan 2021 17:28:40 +0100 Message-ID: Subject: Re: [PATCH v2 08/14] kasan: add compiler barriers to KUNIT_EXPECT_KASAN_FAIL To: Andrey Konovalov Cc: Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Andrew Morton , Will Deacon , Andrey Ryabinin , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev , Linux ARM , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 13 Jan 2021 at 17:22, Andrey Konovalov wrote: > > It might not be obvious to the compiler that the expression must be > executed between writing and reading to fail_data. In this case, the > compiler might reorder or optimize away some of the accesses, and > the tests will fail. > > Add compiler barriers around the expression in KUNIT_EXPECT_KASAN_FAIL > and use READ/WRITE_ONCE() for accessing fail_data fields. > > Link: https://linux-review.googlesource.com/id/I046079f48641a1d36fe627fc8827a9249102fd50 > Signed-off-by: Andrey Konovalov Reviewed-by: Marco Elver > --- > lib/test_kasan.c | 17 ++++++++++++----- > mm/kasan/report.c | 2 +- > 2 files changed, 13 insertions(+), 6 deletions(-) > > diff --git a/lib/test_kasan.c b/lib/test_kasan.c > index 5c8aa3a5ce93..283feda9882a 100644 > --- a/lib/test_kasan.c > +++ b/lib/test_kasan.c > @@ -68,23 +68,30 @@ static void kasan_test_exit(struct kunit *test) > * normally auto-disabled. When this happens, this test handler reenables > * tag checking. As tag checking can be only disabled or enabled per CPU, this > * handler disables migration (preemption). > + * > + * Since the compiler doesn't see that the expression can change the fail_data > + * fields, it can reorder or optimize away the accesses to those fields. > + * Use READ/WRITE_ONCE() for the accesses and compiler barriers around the > + * expression to prevent that. > */ > #define KUNIT_EXPECT_KASAN_FAIL(test, expression) do { \ > if (IS_ENABLED(CONFIG_KASAN_HW_TAGS)) \ > migrate_disable(); \ > - fail_data.report_expected = true; \ > - fail_data.report_found = false; \ > + WRITE_ONCE(fail_data.report_expected, true); \ > + WRITE_ONCE(fail_data.report_found, false); \ > kunit_add_named_resource(test, \ > NULL, \ > NULL, \ > &resource, \ > "kasan_data", &fail_data); \ > + barrier(); \ > expression; \ > + barrier(); \ > KUNIT_EXPECT_EQ(test, \ > - fail_data.report_expected, \ > - fail_data.report_found); \ > + READ_ONCE(fail_data.report_expected), \ > + READ_ONCE(fail_data.report_found)); \ > if (IS_ENABLED(CONFIG_KASAN_HW_TAGS)) { \ > - if (fail_data.report_found) \ > + if (READ_ONCE(fail_data.report_found)) \ > hw_enable_tagging(); \ > migrate_enable(); \ > } \ > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index e93d7973792e..234f35a84f19 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -331,7 +331,7 @@ static void kasan_update_kunit_status(struct kunit *cur_test) > } > > kasan_data = (struct kunit_kasan_expectation *)resource->data; > - kasan_data->report_found = true; > + WRITE_ONCE(kasan_data->report_found, true); > kunit_put_resource(resource); > } > #endif /* IS_ENABLED(CONFIG_KUNIT) */ > -- > 2.30.0.284.gd98b1dd5eaa7-goog >