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=-13.6 required=3.0 tests=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 354E7C433DF for ; Tue, 23 Jun 2020 07:18:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E93D0206B7 for ; Tue, 23 Jun 2020 07:18:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="GFGAJQQi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E93D0206B7 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 6A4B06B0008; Tue, 23 Jun 2020 03:18:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 655416B000A; Tue, 23 Jun 2020 03:18:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 56AB06B000C; Tue, 23 Jun 2020 03:18:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0109.hostedemail.com [216.40.44.109]) by kanga.kvack.org (Postfix) with ESMTP id 3C5126B0008 for ; Tue, 23 Jun 2020 03:18:07 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 065572C8F for ; Tue, 23 Jun 2020 07:18:07 +0000 (UTC) X-FDA: 76959622614.17.tiger59_5507ce526e39 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id D1241180D0783 for ; Tue, 23 Jun 2020 07:18:06 +0000 (UTC) X-HE-Tag: tiger59_5507ce526e39 X-Filterd-Recvd-Size: 5985 Received: from mail-oi1-f195.google.com (mail-oi1-f195.google.com [209.85.167.195]) by imf44.hostedemail.com (Postfix) with ESMTP for ; Tue, 23 Jun 2020 07:18:06 +0000 (UTC) Received: by mail-oi1-f195.google.com with SMTP id i74so18023055oib.0 for ; Tue, 23 Jun 2020 00:18:06 -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=/MteRsl9kXDCB4cggamm2Lh5J0tgrSbPos+TELxySHU=; b=GFGAJQQi1vlgS574df9wkmnHdutzQejXSmLQL6TuOhZHz6YbMAOJTWzBCXcY59KdvP fQhRMrcRfRBrKyNy9fr1lUbZEUNWmeG0bb4Bvmf2Znl/9fkT4uXgv3iyba7n8S5rDxMn ZM6ua0HAquw55QT8cERj8zpuUDUKpHpcaHyAK1lm8hp5Y3Gp81evklhU+GiWbsisBz+E 8paTIfD66ibjOO/n1un/JaDhDU8fAD09sBWHJz3tpxUTARKmqTu+sMPT2JOtIIcOmMe9 7VFZvn4/fD7BqLOzTcAzc365IA23qsmDECsyMCrd3IO0GtN5NCFJrv+r0q1h/ld3MbTk DGTg== 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=/MteRsl9kXDCB4cggamm2Lh5J0tgrSbPos+TELxySHU=; b=TBvuHtwAk41s0WUaLDweJ6uGshk/s0SlAorYizg7NnvPMWKEH7/4WkNK/VVEiaeye7 /zwdCGvCC1J80oC+9rq7mzrpuHf+fBtwxtByS4BZKGGd5VWYg5DLmeJsMuk4mjMO9sDB +rlww9F63I14pY/5XWTqQ0V7MDhxDBRw0kAkUD2xSXdVqoEgNa0G53o8AojpSbCuS510 tHFy9stKydiC33VqJV0MezIT9QPzUm523igSjnMQKClUEK8kMSXBPY2WVNWD0tDT5W7o PEzSt8AcPYx5aGxA48kMblxmBE5jP2soIpX4UPkjMDDtTloCNMYeU8F+ivIMIfIphdQY Apow== X-Gm-Message-State: AOAM531UicufcC2p+HFErR0Obs00LVaoTt2c99zdxyqCoxpvlvWIxhxE b1ypAhR5AiGO4vbBPT+i0j1YB+ZNExLNJSiF2lAj8A== X-Google-Smtp-Source: ABdhPJzBKXUo1WrxeNiIlTCMmGHuyvPThGqyPnmJVDrgKnV893ty/BBXSgNpVvwHEzdELkPKBcmoE6xkBS15DRWd09M= X-Received: by 2002:a05:6808:34f:: with SMTP id j15mr15871155oie.121.1592896685597; Tue, 23 Jun 2020 00:18:05 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Marco Elver Date: Tue, 23 Jun 2020 09:17:54 +0200 Message-ID: Subject: Re: Kernel hardening project suggestion: Normalizing ->ctor slabs and TYPESAFE_BY_RCU slabs To: Dmitry Vyukov Cc: Jann Horn , Kernel Hardening , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Linux-MM , Andrey Konovalov , Will Deacon , kasan-dev , Kees Cook , Alexander Potapenko Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: D1241180D0783 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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 Tue, 23 Jun 2020 at 08:45, Dmitry Vyukov wrote: > > On Tue, Jun 23, 2020 at 8:26 AM Jann Horn wrote: > > > > Hi! > > > > Here's a project idea for the kernel-hardening folks: > > > > The slab allocator interface has two features that are problematic for > > security testing and/or hardening: > > > > - constructor slabs: These things come with an object constructor > > that doesn't run when an object is allocated, but instead when the > > slab allocator grabs a new page from the page allocator. This is > > problematic for use-after-free detection mechanisms such as HWASAN and > > Memory Tagging, which can only do their job properly if the address of > > an object is allowed to change every time the object is > > freed/reallocated. (You can't change the address of an object without > > reinitializing the entire object because e.g. an empty list_head > > points to itself.) > > > > - RCU slabs: These things basically permit use-after-frees by design, > > and stuff like ASAN/HWASAN/Memory Tagging essentially doesn't work on > > them. > > > > > > It would be nice to have a config flag or so that changes the SLUB > > allocator's behavior such that these slabs can be instrumented > > properly. Something like: > > > > - Let calculate_sizes() reserve space for an rcu_head on each object > > in TYPESAFE_BY_RCU slabs, make kmem_cache_free() redirect to > > call_rcu() for these slabs, and remove most of the other > > special-casing, so that KASAN can instrument these slabs. > > - For all constructor slabs, let slab_post_alloc_hook() call the > > ->ctor() function on each allocated object, so that Memory Tagging and > > HWASAN will work on them. > > Hi Jann, > > Both things sound good to me. I think we considered doing the ctor's > change with KASAN, but we did not get anywhere. The only argument > against it I remember now was "performance", but it's not that > important if this mode is enabled only with KASAN and other debugging > tools. Performance is definitely not as important as missing bugs. The > additional code complexity for ctors change should be minimal. > The rcu change would also be useful, but I would assume it will be larger. > Please add them to [1], that's KASAN laundry list. > > +Alex, Marco, will it be useful for KFENCE [2] as well? Do ctors/rcu > affect KFENCE? Will we need any special handling for KFENCE? > I assume it will also be useful for KMSAN b/c we can re-mark objects > as uninitialized only after they have been reallocated. Yes, we definitely need to handle TYPESAFE_BY_RCU. > [1] https://bugzilla.kernel.org/buglist.cgi?bug_status=__open__&component=Sanitizers&list_id=1063981&product=Memory%20Management > [2] https://github.com/google/kasan/commits/kfence