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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 AA6D0C5B57B for ; Sat, 29 Jun 2019 23:43:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8177D20828 for ; Sat, 29 Jun 2019 23:43:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561851817; bh=6Ls1mmfTCbzFx4Rzb3UhYmFEV6me19aFFOMlTGuTuMY=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=fssdHj13LPaT0NC7dfNSGV9inttSZPyTOKRkDcEGLQndLvRvCXtPTlHUI0OuQjIr6 +VQpHA5myGBeEYpmBVWywrBqS+S0HmQ2NHTGZ+EFLChYQ1ryQJ7bWeM4/DOdApXIrU XN4e4MXF2EIVSIEFHLwTAzj+Ij1inFe4TKa5yKAU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726977AbfF2Xnc (ORCPT ); Sat, 29 Jun 2019 19:43:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:56678 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726954AbfF2Xnc (ORCPT ); Sat, 29 Jun 2019 19:43:32 -0400 Received: from mail-wr1-f42.google.com (mail-wr1-f42.google.com [209.85.221.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8D67A21783 for ; Sat, 29 Jun 2019 23:43:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561851810; bh=6Ls1mmfTCbzFx4Rzb3UhYmFEV6me19aFFOMlTGuTuMY=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=ItDaQR+YFwM+zUWyq0SEZyW3Pn6dapJHuivHM4jw8jYIYATlvNCFgUOVSyHA15NNw AEZK10pv6CFtIGXjIbUG7AXyDMsOmLHnHbBJ/EnoIw6y8yuhITck+ydss7eXTQlmm2 HPBufIxfXjHuzQKQSM+5jkAcCFZ77DOpPDDnzdOY= Received: by mail-wr1-f42.google.com with SMTP id p11so9913276wre.7 for ; Sat, 29 Jun 2019 16:43:30 -0700 (PDT) X-Gm-Message-State: APjAAAWhCMN9MtqGb64LRCrpYLY/ZW2rDoOkFyAxYtOVFWOIPQ+OqC+z Unqnk0/ZfDdS3h6iPjHRl/2dB7A5IL5MddQMgc8nsw== X-Google-Smtp-Source: APXvYqy1lccm+W/+pWlsgMcG6L5G1lNH4IFhUO6vjgvEXUaNIhYR7BWWHlgDd5MOsBd1OpDkbJ+gIKmRECPoUjBLpFU= X-Received: by 2002:adf:dd0f:: with SMTP id a15mr10561378wrm.265.1561851809106; Sat, 29 Jun 2019 16:43:29 -0700 (PDT) MIME-Version: 1.0 References: <20190628194158.2431-1-yu-cheng.yu@intel.com> <20190628194158.2431-2-yu-cheng.yu@intel.com> In-Reply-To: <20190628194158.2431-2-yu-cheng.yu@intel.com> From: Andy Lutomirski Date: Sat, 29 Jun 2019 16:43:18 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 2/3] Introduce arch_prctl(ARCH_X86_CET_MARK_LEGACY_CODE) To: Yu-cheng Yu Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jun 28, 2019, at 12:41 PM, Yu-cheng Yu wrote: > > The CET legacy code bitmap covers the whole user-mode address space and i= s > located at the top of the user-mode address space. It is allocated only > when the first time arch_prctl(ARCH_X86_MARK_LEGACY_CODE) is called from > an application. > > Introduce: > > arch_prctl(ARCH_X86_MARK_LEGACY_CODE, unsigned long *buf) > Mark an address range as IBT legacy code. How about defining a struct for this? The change log should discuss where the bitmap goes and how it=E2=80=99s al= located. > +static int alloc_bitmap(void) > +{ > + unsigned long addr; > + u64 msr_ia32_u_cet; > + > + addr =3D do_mmap_locked(NULL, IBT_BITMAP_ADDR, IBT_BITMAP_SIZE, > + PROT_READ | PROT_WRITE, > + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, > + VM_IBT | VM_NORESERVE, NULL); > + > + if (IS_ERR((void *)addr)) > + return addr; > + > + current->thread.cet.ibt_bitmap_addr =3D addr; addr is a constant. Why are you storing it? If it ends up not being constant, you should wire up mremap like the vDSO does. > +static int set_user_bits(unsigned long __user *buf, unsigned long buf_si= ze, > + unsigned long start_bit, unsigned long end_bit, unsigned lo= ng set) > +{ > + unsigned long start_ul, end_ul, total_ul; > + int i, j, r; > + > + if (round_up(end_bit, BITS_PER_BYTE) / BITS_PER_BYTE > buf_size) > + end_bit =3D buf_size * BITS_PER_BYTE - 1; > + > + start_ul =3D start_bit / BITS_PER_LONG; > + end_ul =3D end_bit / BITS_PER_LONG; > + total_ul =3D (end_ul - start_ul + 1); > + > + i =3D start_bit % BITS_PER_LONG; > + j =3D end_bit % BITS_PER_LONG; > + > + r =3D 0; > + put_user_try { put_user_try is obsolete. Just use get_user(), etc. Also, I must be missing something fundamental, because this series claims that user code can't write directly to the bitmap. This means that this entire function shouldn't work at all.