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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 1A384C433DF for ; Tue, 23 Jun 2020 12:38:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AE2F12072E for ; Tue, 23 Jun 2020 12:38:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AE2F12072E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0FF796B0002; Tue, 23 Jun 2020 08:38:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0AE116B0005; Tue, 23 Jun 2020 08:38:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E903D6B0006; Tue, 23 Jun 2020 08:38:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0223.hostedemail.com [216.40.44.223]) by kanga.kvack.org (Postfix) with ESMTP id CD3EF6B0002 for ; Tue, 23 Jun 2020 08:38:42 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 3C83B2C81 for ; Tue, 23 Jun 2020 12:38:42 +0000 (UTC) X-FDA: 76960430484.26.cows96_2603b4926e3b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id 0BE621804B65C for ; Tue, 23 Jun 2020 12:38:42 +0000 (UTC) X-HE-Tag: cows96_2603b4926e3b X-Filterd-Recvd-Size: 7942 Received: from mail-qk1-f195.google.com (mail-qk1-f195.google.com [209.85.222.195]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Tue, 23 Jun 2020 12:38:41 +0000 (UTC) Received: by mail-qk1-f195.google.com with SMTP id z63so6511160qkb.8 for ; Tue, 23 Jun 2020 05:38:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=sTHxvMyi6xXHEDj5tKcB1PxfIVdWXw+JPrgVRYwiDBQ=; b=svYWjFTRelSHa2pS9RlgeLM6T4Ah7gYvyEuJG47tSXh/WQ0N4oNXtJoF34Hnsol0gZ LpWfE1Gb0YSqSD7G/7PrGj6WjPFrUOfv4vj+189vatdOp1RW0Mun6DMIB8Z7NKVXPZVs Uj4XVq00b0G8LBDGEXajruYQccgS1cWVQNywNOFk4XoW+Mj5yWgkyP77fAi2gBKNroCr zDIiA408yfQAwyseup89iEG8gHr4LKknJlhRvl/j98lDzxJL5bSigwVtqm3XVO/cRmY8 rA3B/IkF0jtATjbATUyAm7ZfQ0Iur9Rm7QVAnJsBADZ8VHZcREqWgO8xF93uBIlzvonm r7kw== X-Gm-Message-State: AOAM5300/aZEAJJWATIxd6Bgyo25mXUxgzweMQg1tLp5aXXhvuq7wqNa KOCH17GnQXPICIJARvCCjdI= X-Google-Smtp-Source: ABdhPJyf4YApQi2W+KxMgNcaGYzpYsr/thux7I1WZZKaOtTMFb1sLHKlEZRcH55X3Y4zM+cNdtQWfw== X-Received: by 2002:a05:620a:57a:: with SMTP id p26mr19288448qkp.386.1592915920944; Tue, 23 Jun 2020 05:38:40 -0700 (PDT) Received: from [10.9.0.18] ([185.248.161.177]) by smtp.gmail.com with ESMTPSA id o12sm466100qtl.48.2020.06.23.05.38.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Jun 2020 05:38:40 -0700 (PDT) Reply-To: alex.popov@linux.com Subject: Re: [PATCH v4 3/5] stack: Optionally randomize kernel stack offset each syscall To: Kees Cook , Thomas Gleixner Cc: Elena Reshetova , x86@kernel.org, Andy Lutomirski , Peter Zijlstra , Catalin Marinas , Will Deacon , Mark Rutland , Alexander Potapenko , Ard Biesheuvel , Jann Horn , kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200622193146.2985288-1-keescook@chromium.org> <20200622193146.2985288-4-keescook@chromium.org> From: Alexander Popov Autocrypt: addr=alex.popov@linux.com; prefer-encrypt=mutual; keydata= mQINBFX15q4BEADZartsIW3sQ9R+9TOuCFRIW+RDCoBWNHhqDLu+Tzf2mZevVSF0D5AMJW4f UB1QigxOuGIeSngfmgLspdYe2Kl8+P8qyfrnBcS4hLFyLGjaP7UVGtpUl7CUxz2Hct3yhsPz ID/rnCSd0Q+3thrJTq44b2kIKqM1swt/F2Er5Bl0B4o5WKx4J9k6Dz7bAMjKD8pHZJnScoP4 dzKPhrytN/iWM01eRZRc1TcIdVsRZC3hcVE6OtFoamaYmePDwWTRhmDtWYngbRDVGe3Tl8bT 7BYN7gv7Ikt7Nq2T2TOfXEQqr9CtidxBNsqFEaajbFvpLDpUPw692+4lUbQ7FL0B1WYLvWkG cVysClEyX3VBSMzIG5eTF0Dng9RqItUxpbD317ihKqYL95jk6eK6XyI8wVOCEa1V3MhtvzUo WGZVkwm9eMVZ05GbhzmT7KHBEBbCkihS+TpVxOgzvuV+heCEaaxIDWY/k8u4tgbrVVk+tIVG 99v1//kNLqd5KuwY1Y2/h2MhRrfxqGz+l/f/qghKh+1iptm6McN//1nNaIbzXQ2Ej34jeWDa xAN1C1OANOyV7mYuYPNDl5c9QrbcNGg3D6gOeGeGiMn11NjbjHae3ipH8MkX7/k8pH5q4Lhh Ra0vtJspeg77CS4b7+WC5jlK3UAKoUja3kGgkCrnfNkvKjrkEwARAQABtCZBbGV4YW5kZXIg UG9wb3YgPGFsZXgucG9wb3ZAbGludXguY29tPokCVwQTAQgAQQIbIwIeAQIXgAULCQgHAwUV CgkICwUWAgMBAAIZARYhBLl2JLAkAVM0bVvWTo4Oneu8fo+qBQJdehKcBQkLRpLuAAoJEI4O neu8fo+qrkgP/jS0EhDnWhIFBnWaUKYWeiwR69DPwCs/lNezOu63vg30O9BViEkWsWwXQA+c SVVTz5f9eB9K2me7G06A3U5AblOJKdoZeNX5GWMdrrGNLVISsa0geXNT95TRnFqE1HOZJiHT NFyw2nv+qQBUHBAKPlk3eL4/Yev/P8w990Aiiv6/RN3IoxqTfSu2tBKdQqdxTjEJ7KLBlQBm 5oMpm/P2Y/gtBiXRvBd7xgv7Y3nShPUDymjBnc+efHFqARw84VQPIG4nqVhIei8gSWps49DX kp6v4wUzUAqFo+eh/ErWmyBNETuufpxZnAljtnKpwmpFCcq9yfcMlyOO9/viKn14grabE7qE 4j3/E60wraHu8uiXJlfXmt0vG16vXb8g5a25Ck09UKkXRGkNTylXsAmRbrBrA3Moqf8QzIk9 p+aVu/vFUs4ywQrFNvn7Qwt2hWctastQJcH3jrrLk7oGLvue5KOThip0SNicnOxVhCqstjYx KEnzZxtna5+rYRg22Zbfg0sCAAEGOWFXjqg3hw400oRxTW7IhiE34Kz1wHQqNif0i5Eor+TS 22r9iF4jUSnk1jaVeRKOXY89KxzxWhnA06m8IvW1VySHoY1ZG6xEZLmbp3OuuFCbleaW07OU 9L8L1Gh1rkAz0Fc9eOR8a2HLVFnemmgAYTJqBks/sB/DD0SuuQINBFX15q4BEACtxRV/pF1P XiGSbTNPlM9z/cElzo/ICCFX+IKg+byRvOMoEgrzQ28ah0N5RXQydBtfjSOMV1IjSb3oc23z oW2J9DefC5b8G1Lx2Tz6VqRFXC5OAxuElaZeoowV1VEJuN3Ittlal0+KnRYY0PqnmLzTXGA9 GYjw/p7l7iME7gLHVOggXIk7MP+O+1tSEf23n+dopQZrkEP2BKSC6ihdU4W8928pApxrX1Lt tv2HOPJKHrcfiqVuFSsb/skaFf4uveAPC4AausUhXQVpXIg8ZnxTZ+MsqlwELv+Vkm/SNEWl n0KMd58gvG3s0bE8H2GTaIO3a0TqNKUY16WgNglRUi0WYb7+CLNrYqteYMQUqX7+bB+NEj/4 8dHw+xxaIHtLXOGxW6zcPGFszaYArjGaYfiTTA1+AKWHRKvD3MJTYIonphy5EuL9EACLKjEF v3CdK5BLkqTGhPfYtE3B/Ix3CUS1Aala0L+8EjXdclVpvHQ5qXHs229EJxfUVf2ucpWNIUdf lgnjyF4B3R3BFWbM4Yv8QbLBvVv1Dc4hZ70QUXy2ZZX8keza2EzPj3apMcDmmbklSwdC5kYG EFT4ap06R2QW+6Nw27jDtbK4QhMEUCHmoOIaS9j0VTU4fR9ZCpVT/ksc2LPMhg3YqNTrnb1v RVNUZvh78zQeCXC2VamSl9DMcwARAQABiQI8BBgBCAAmAhsMFiEEuXYksCQBUzRtW9ZOjg6d 67x+j6oFAl16ErcFCQtGkwkACgkQjg6d67x+j6q7zA/+IsjSKSJypgOImN9LYjeb++7wDjXp qvEpq56oAn21CvtbGus3OcC0hrRtyZ/rC5Qc+S5SPaMRFUaK8S3j1vYC0wZJ99rrmQbcbYMh C2o0k4pSejaINmgyCajVOhUhln4IuwvZke1CLfXe1i3ZtlaIUrxfXqfYpeijfM/JSmliPxwW BRnQRcgS85xpC1pBUMrraxajaVPwu7hCTke03v6bu8zSZlgA1rd9E6KHu2VNS46VzUPjbR77 kO7u6H5PgQPKcuJwQQ+d3qa+5ZeKmoVkc2SuHVrCd1yKtAMmKBoJtSku1evXPwyBzqHFOInk mLMtrWuUhj+wtcnOWxaP+n4ODgUwc/uvyuamo0L2Gp3V5ItdIUDO/7ZpZ/3JxvERF3Yc1md8 5kfflpLzpxyl2fKaRdvxr48ZLv9XLUQ4qNuADDmJArq/+foORAX4BBFWvqZQKe8a9ZMAvGSh uoGUVg4Ks0uC4IeG7iNtd+csmBj5dNf91C7zV4bsKt0JjiJ9a4D85dtCOPmOeNuusK7xaDZc gzBW8J8RW+nUJcTpudX4TC2SGeAOyxnM5O4XJ8yZyDUY334seDRJWtS4wRHxpfYcHKTewR96 IsP1USE+9ndu6lrMXQ3aFsd1n1m1pfa/y8hiqsSYHy7JQ9Iuo9DxysOj22UNOmOE+OYPK48D j3lCqPk= Message-ID: Date: Tue, 23 Jun 2020 15:38:32 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200622193146.2985288-4-keescook@chromium.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 0BE621804B65C X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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 22.06.2020 22:31, Kees Cook wrote: > As Linux kernel stack protections have been constantly improving > (vmap-based stack allocation with guard pages, removal of thread_info, > STACKLEAK), attackers have had to find new ways for their exploits > to work. They have done so, continuing to rely on the kernel's stack > determinism, in situations where VMAP_STACK and THREAD_INFO_IN_TASK_STRUCT > were not relevant. For example, the following recent attacks would have > been hampered if the stack offset was non-deterministic between syscalls: > > https://repositorio-aberto.up.pt/bitstream/10216/125357/2/374717.pdf > (page 70: targeting the pt_regs copy with linear stack overflow) > > https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html > (leaked stack address from one syscall as a target during next syscall) > > The main idea is that since the stack offset is randomized on each system > call, it is harder for an attack to reliably land in any particular place > on the thread stack, even with address exposures, as the stack base will > change on the next syscall. Also, since randomization is performed after > placing pt_regs, the ptrace-based approach[1] to discover the randomized > offset during a long-running syscall should not be possible. Hello Kees! I would recommend to disable CONFIG_STACKLEAK_METRICS if kernel stack offset randomization is enabled. It is a debugging feature that provides information about kernel stack usage. That info can be useful for calculating the random offset. I would also recommend to check: there might be other kernel features for debugging or getting statistics that can be used to disclose the random stack offset. Best regards, Alexander