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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, 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 8DE0CC04ABB for ; Thu, 13 Sep 2018 08:37:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2613D20C0A for ; Thu, 13 Sep 2018 08:37:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="pDUeEFhd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2613D20C0A Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727795AbeIMNpt (ORCPT ); Thu, 13 Sep 2018 09:45:49 -0400 Received: from mail-it0-f65.google.com ([209.85.214.65]:34457 "EHLO mail-it0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726932AbeIMNps (ORCPT ); Thu, 13 Sep 2018 09:45:48 -0400 Received: by mail-it0-f65.google.com with SMTP id x79-v6so1168210ita.1 for ; Thu, 13 Sep 2018 01:37:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=6Bb2A5n9HnIKxxiAYVSOIkWwld1KVWNHVDF2g+uXCCM=; b=pDUeEFhdU3zyhg1x/HiI0W40JAo8WB6SaePlNyo8Q0n0V/q7tljZewVt2zTb4bq/xI MeT4IY7fqyJhiSJ/gr44MUgCFAkCz/PWQuaE5JHdKHNfNZ0Y8wTo5s7okWcbHhdz6dVq Niu7d2qmciT/wAlXFO3kbI9Q8JDMcWEL90exZVIruYcyGk/x6GuQOG6L4y7ZD0L7fgB9 IrhCzO38rx8QlFqc6Vz35yF7UO5w7bx3EKO69D99ARAyuEbRlmrFQMlJ6ekhVmQYywJM 6wlYnlASoI34Qk5Ptf+olmJ4ka7wfm/zD4tQ2iPbFzDPq/lav+saA1jtaPkswb1CbIKr 2T2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=6Bb2A5n9HnIKxxiAYVSOIkWwld1KVWNHVDF2g+uXCCM=; b=RrJ9C4KglYHj+JaOCE7/h+ic5p2+P1GiP+gPQJ6AaHK/tV0oZIwf+C6lt0Ogls/cbe U6hXFDsbvEUiCVr5oN6jCtUGhz4JdSltPs9Fh3hx4HUTeKpOJAwMkqkRjDPbXgoqS/Un jAh+uuf58Soe2VdAF2hEuXP4x3BCcKo6iFRQOy4QpFNS0Rm2VU7ACGVDKZuVj1iszmOW fwarXgA3cdTEuk1F2DX8/2Z14xFPZEnX86Kg5W5hrM44h9968uBMAh+bmuEL9Ojkwz8M 0SJsnQxROfe7xEw2f5JjVmqoeCBDajDGPSa44vRSop+l6tblRNC27mjc+NdOBwT3bdgZ ijKw== X-Gm-Message-State: APzg51DRASuOkMcw8oFZFfoMc+kHfU3qv2/UnUPXQj5UbHQq4rf33ePi g/RHf781NNGR8BX4mmTh4DU0F4UAoBB47SWjMS8+1A== X-Google-Smtp-Source: ANB0VdYcmxf7OZhQotgjLkFTdL4h4ljh5jDVkU/4X7vMHzZYyDFzjYTfm91uFkN3hCc9V3yXzXUXA9iH+sf/CAOba00= X-Received: by 2002:a02:4009:: with SMTP id n9-v6mr5701091jaa.19.1536827840777; Thu, 13 Sep 2018 01:37:20 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a02:5942:0:0:0:0:0 with HTTP; Thu, 13 Sep 2018 01:37:00 -0700 (PDT) In-Reply-To: References: From: Dmitry Vyukov Date: Thu, 13 Sep 2018 10:37:00 +0200 Message-ID: Subject: Re: [PATCH v6 15/18] khwasan, arm64: add brk handler for inline instrumentation To: Jann Horn Cc: Andrey Konovalov , Andrey Ryabinin , Alexander Potapenko , Catalin Marinas , Will Deacon , Christoph Lameter , Andrew Morton , Mark Rutland , Nick Desaulniers , Marc Zyngier , Dave Martin , Ard Biesheuvel , "Eric W. Biederman" , Ingo Molnar , Paul Lawrence , Geert Uytterhoeven , Arnd Bergmann , "Kirill A . Shutemov" , Greg Kroah-Hartman , Kate Stewart , Mike Rapoport , kasan-dev , linux-doc@vger.kernel.org, kernel list , Linux ARM , linux-sparse@vger.kernel.org, Linux-MM , "open list:KERNEL BUILD + fi..." , Kostya Serebryany , Evgenii Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Mark Brand , Chintan Pandya , Vishwath Mohan 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 Wed, Sep 12, 2018 at 7:39 PM, Jann Horn wrote: > On Wed, Sep 12, 2018 at 7:16 PM Dmitry Vyukov wrote: >> On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov wrote: > [...] >> > +static int khwasan_handler(struct pt_regs *regs, unsigned int esr) >> > +{ >> > + bool recover = esr & KHWASAN_ESR_RECOVER; >> > + bool write = esr & KHWASAN_ESR_WRITE; >> > + size_t size = KHWASAN_ESR_SIZE(esr); >> > + u64 addr = regs->regs[0]; >> > + u64 pc = regs->pc; >> > + >> > + if (user_mode(regs)) >> > + return DBG_HOOK_ERROR; >> > + >> > + kasan_report(addr, size, write, pc); >> > + >> > + /* >> > + * The instrumentation allows to control whether we can proceed after >> > + * a crash was detected. This is done by passing the -recover flag to >> > + * the compiler. Disabling recovery allows to generate more compact >> > + * code. >> > + * >> > + * Unfortunately disabling recovery doesn't work for the kernel right >> > + * now. KHWASAN reporting is disabled in some contexts (for example when >> > + * the allocator accesses slab object metadata; same is true for KASAN; >> > + * this is controlled by current->kasan_depth). All these accesses are >> > + * detected by the tool, even though the reports for them are not >> > + * printed. >> > + * >> > + * This is something that might be fixed at some point in the future. >> > + */ >> > + if (!recover) >> > + die("Oops - KHWASAN", regs, 0); >> >> Why die and not panic? Die seems to be much less used function, and it >> calls panic anyway, and we call panic in kasan_report if panic_on_warn >> is set. > > die() is vaguely equivalent to BUG(); die() and BUG() normally only > terminate the current process, which may or may not leave the system > somewhat usable, while panic() always brings down the whole system. > AFAIK panic() shouldn't be used unless you're in some very low-level > code where you know that trying to just kill the current process can't > work and the entire system is broken beyond repair. > > If KASAN traps on some random memory access, there's a good chance > that just killing the current process will allow at least parts of the > system to continue. I'm not sure whether BUG() or die() is more > appropriate here, but I think it definitely should not be a panic(). Nick, do you know if die() will be enough to catch problems on Android phones? panic_on_warn would turn this into panic, but I guess one does not want panic_on_warn on a canary phone.