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=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 6748CC433E4 for ; Fri, 17 Jul 2020 00:20:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 44425207DD for ; Fri, 17 Jul 2020 00:20:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594945218; bh=dynZiMT160fFV318XcHN8vJ1LFq3IdJmZE81Qj67JHY=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=fVznowvvfJuGFFQjaT1h+lZDUMWBbT7FnI3JgbJVUDmgiBqITN6mOXwfRWrnPuuHY 8IyYPrr4KClm4YqQ8qPIWgv3DlEw1TxYg9o8GrIfRqSloCoBaE06AlYrLlx/z3nkU9 GmPL88xhyny0UJ29swElPdGY+hd9wFjibmV622uQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726393AbgGQAUQ (ORCPT ); Thu, 16 Jul 2020 20:20:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:43720 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726125AbgGQAUQ (ORCPT ); Thu, 16 Jul 2020 20:20:16 -0400 Received: from mail-wr1-f47.google.com (mail-wr1-f47.google.com [209.85.221.47]) (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 58A72207EA for ; Fri, 17 Jul 2020 00:20:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594945215; bh=dynZiMT160fFV318XcHN8vJ1LFq3IdJmZE81Qj67JHY=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=BXz3QKqi5cKE5fh3RKhpo+RLAtmQYAk5eW485twQ4Cvsc8Kzi0ysV+OPGw4+KH5zJ ltvZJtC16tfj6Wse9+LLFHiaYZNJh550ZYV89+HfejCZ2PYSi+p0c9Aog9mOQOMq+Y JUc+qCzzvaADEOiiSFb5qJG3qaTvS0TS+wqCxoHs= Received: by mail-wr1-f47.google.com with SMTP id j4so9076049wrp.10 for ; Thu, 16 Jul 2020 17:20:15 -0700 (PDT) X-Gm-Message-State: AOAM5334qQnkICC419YZOe46CUQ0hNiyuCHy4LGl9h9HmqdrUaIC7kDw xL/gxZj1bOYzwFYesWcA/2GWMGLMXO086DpLFoyJ8g== X-Google-Smtp-Source: ABdhPJyFwQ9TS/dW0gUFTXF5Hg6RwZdmG8iOGVpkOopW3ph3siXASHwq1e23sAvzryIIoeiFZKhOnjnIRg9xnOzP4dE= X-Received: by 2002:adf:f707:: with SMTP id r7mr7398196wrp.70.1594945213901; Thu, 16 Jul 2020 17:20:13 -0700 (PDT) MIME-Version: 1.0 References: <20200716193141.4068476-1-krisman@collabora.com> <20200716193141.4068476-2-krisman@collabora.com> In-Reply-To: <20200716193141.4068476-2-krisman@collabora.com> From: Andy Lutomirski Date: Thu, 16 Jul 2020 17:20:02 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4 1/2] kernel: Implement selective syscall userspace redirection To: Gabriel Krisman Bertazi Cc: Thomas Gleixner , LKML , kernel@collabora.com, Matthew Wilcox , Andrew Lutomirski , Paul Gofman , Kees Cook , "open list:KERNEL SELFTEST FRAMEWORK" , Shuah Khan Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 16, 2020 at 12:31 PM Gabriel Krisman Bertazi wrote: > This is quite nice. I have a few comments, though: You mentioned rt_sigreturn(). Should this automatically exempt the kernel-provided signal restorer on architectures (e.g. x86_32) that provide one? The amount of syscall entry wiring that arches need to do is IMO already a bit out of hand. Should we instead rename TIF_SECCOMP to TIF_SYSCALL_INTERCEPTION and have one generic callback that handles seccomp and this new thing? > +int do_syscall_user_dispatch(struct pt_regs *regs) > +{ > + struct syscall_user_dispatch *sd = ¤t->syscall_dispatch; > + unsigned long ip = instruction_pointer(regs); > + char state; > + > + if (likely(ip >= sd->dispatcher_start && ip <= sd->dispatcher_end)) > + return 0; > + > + if (likely(sd->selector)) { > + if (unlikely(__get_user(state, sd->selector))) > + do_exit(SIGSEGV); > + > + if (likely(state == 0)) > + return 0; > + > + if (state != 1) > + do_exit(SIGSEGV); This seems a bit extreme and hard to debug if it ever happens.