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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, 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 958DEC433E2 for ; Thu, 10 Sep 2020 15:06:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1DD1E2078B for ; Thu, 10 Sep 2020 15:06:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="d7rj+8Qp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1DD1E2078B 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 6460190001F; Thu, 10 Sep 2020 11:06:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5F5CA90001C; Thu, 10 Sep 2020 11:06:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4E4B390001F; Thu, 10 Sep 2020 11:06:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0002.hostedemail.com [216.40.44.2]) by kanga.kvack.org (Postfix) with ESMTP id 3A41A90001C for ; Thu, 10 Sep 2020 11:06:44 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E5B9A181AEF31 for ; Thu, 10 Sep 2020 15:06:43 +0000 (UTC) X-FDA: 77247478686.13.trail33_2a0eb9c270e7 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 40F101814063F for ; Thu, 10 Sep 2020 15:06:39 +0000 (UTC) X-HE-Tag: trail33_2a0eb9c270e7 X-Filterd-Recvd-Size: 6714 Received: from mail-ot1-f67.google.com (mail-ot1-f67.google.com [209.85.210.67]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Thu, 10 Sep 2020 15:06:38 +0000 (UTC) Received: by mail-ot1-f67.google.com with SMTP id 60so5618095otw.3 for ; Thu, 10 Sep 2020 08:06:38 -0700 (PDT) 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=2DiBsMVuHaQKweeTOQHLBykKJQg8tEScxOxVWMIr6f4=; b=d7rj+8QpSjUscxArZ7XYKcuFoi7B/GFxbmwxY/YeAJFpXkDE4GqonTwAilQRs3eHCr 9wgqUUGp2M2uZqGrS8oyOuUHtC72NS+g+HPsaSoYo3tcxRVgrIlDea7prwP0aii0bjkR WJcgjPHMGb1+5uTKdiVpFY05RsxeiG/It4ZrCaBrC3jeXnxUb3JdE5uIwvrsGaNyS4x7 Dq11bilXPZ9dpQgxS66wkRODkNr/rumXomg4AH7YlQffk8K2MBnEZSd4mbQm+F4nV39/ Hyi0MLbwb0o8rTE3Z9b1JJf241U+CBVEHuof+AYwXeSrnN4RIb7n+OlXgrSBFjT/81j6 ySxQ== 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=2DiBsMVuHaQKweeTOQHLBykKJQg8tEScxOxVWMIr6f4=; b=sdrNJvPKYVQKjcXoNQRvXHvvpAgTvvxdysoKVJDq8zgDyMkDlYksVuvITUUQPvJFS/ KIONwvqITbL7aNEu4ZTu5bDrRKPR1yOwBK/8sFBxV9uF6DkAPA6Z5lTX8hSkNipqH5G7 scbIQev6hW98jgfyYPq+7p+weKJmEeep21OtJcI549p+Owz3pDmSfhWmeDjwlSNZbEwY t8/OjBNZx1N5hUkSU7L1a3i5nYT4/C1aSAZpfxtwr4hHXPaVUcH4Raua4ENSeU69S0yg dLOgTUBWssEws3OwCHPAyKeHtpIsknkdt8/+lwckssvdTNX+afeh2iAzoXBkhaSLL5zU e+CQ== X-Gm-Message-State: AOAM531OWRmfnhWjSgl7KoN8OVUdjBR9i+Hv8Nc2dR3LpQyrwvQHt5Wx ydP/zM1jM6J4nI/l6gdvs2goCh4XxeJWucSFQqpJ7Q== X-Google-Smtp-Source: ABdhPJxdJ+UeiRt911/9A7d8J232d9N9212FdeXDAshArM9b5lcwP3AeLW4qnCw6pMgyGhpwo76X6VTJZQhXKQnltDA= X-Received: by 2002:a9d:3da1:: with SMTP id l30mr4426034otc.233.1599750397232; Thu, 10 Sep 2020 08:06:37 -0700 (PDT) MIME-Version: 1.0 References: <20200907134055.2878499-1-elver@google.com> <20200907134055.2878499-2-elver@google.com> In-Reply-To: From: Marco Elver Date: Thu, 10 Sep 2020 17:06:25 +0200 Message-ID: Subject: Re: [PATCH RFC 01/10] mm: add Kernel Electric-Fence infrastructure To: Dmitry Vyukov Cc: Alexander Potapenko , Andrew Morton , Catalin Marinas , Christoph Lameter , David Rientjes , Joonsoo Kim , Mark Rutland , Pekka Enberg , "H. Peter Anvin" , "Paul E. McKenney" , Andrey Konovalov , Andrey Ryabinin , Andy Lutomirski , Borislav Petkov , Dave Hansen , Eric Dumazet , Greg Kroah-Hartman , Ingo Molnar , Jann Horn , Jonathan Corbet , Kees Cook , Peter Zijlstra , Qian Cai , Thomas Gleixner , Will Deacon , "the arch/x86 maintainers" , "open list:DOCUMENTATION" , LKML , kasan-dev , Linux ARM , Linux-MM Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 40F101814063F X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 Thu, 10 Sep 2020 at 16:58, Dmitry Vyukov wrote: > > On Mon, Sep 7, 2020 at 3:41 PM Marco Elver wrote: > > +config KFENCE_NUM_OBJECTS > > + int "Number of guarded objects available" > > + default 255 > > + range 1 65535 > > + help > > + The number of guarded objects available. For each KFENCE object, 2 > > + pages are required; with one containing the object and two adjacent > > + ones used as guard pages. > > Hi Marco, > > Wonder if you tested build/boot with KFENCE_NUM_OBJECTS=65535? Can a > compiler create such a large object? Indeed, I get a "ld: kernel image bigger than KERNEL_IMAGE_SIZE". Let's lower it to something more reasonable. The main reason to have the limit is to constrain random configs and avoid the inevitable error reports. > > +config KFENCE_FAULT_INJECTION > > + int "Fault injection for stress testing" > > + default 0 > > + depends on EXPERT > > + help > > + The inverse probability with which to randomly protect KFENCE object > > + pages, resulting in spurious use-after-frees. The main purpose of > > + this option is to stress-test KFENCE with concurrent error reports > > + and allocations/frees. A value of 0 disables fault injection. > > I would name this differently. "FAULT_INJECTION" is already taken for > a different thing, so it's a bit confusing. > KFENCE_DEBUG_SOMETHING may be a better name. > It would also be good to make it very clear in the short description > that this is for testing of KFENCE itself. When I configure syzbot I > routinely can't figure out if various DEBUG configs detect user > errors, or enable additional unit tests, or something else. Makes sense, we'll change the name. > Maybe it should depend on DEBUG_KERNEL as well? EXPERT selects DEBUG_KERNEL, so depending on DEBUG_KERNEL doesn't make sense. > > +/* > > + * Get the canary byte pattern for @addr. Use a pattern that varies based on the > > + * lower 3 bits of the address, to detect memory corruptions with higher > > + * probability, where similar constants are used. > > + */ > > +#define KFENCE_CANARY_PATTERN(addr) ((u8)0xaa ^ (u8)((unsigned long)addr & 0x7)) > > (addr) in macro body Done for v2. > > + seq_con_printf(seq, > > + "kfence-#%zd [0x" PTR_FMT "-0x" PTR_FMT > > PTR_FMT is only used in this file, should it be declared in report.c? It's also used by the test. > Please post example reports somewhere. It's hard to figure out all > details of the reporting/formatting. They can be seen in Documentation added later in the series (also viewable here: https://github.com/google/kasan/blob/kfence/Documentation/dev-tools/kfence.rst) Thank you! -- Marco