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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 37A6BC4363D for ; Thu, 24 Sep 2020 21:41:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB89D239CF for ; Thu, 24 Sep 2020 21:41:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="s9aB8dgH"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="vCvDhw1z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726693AbgIXVl3 (ORCPT ); Thu, 24 Sep 2020 17:41:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39892 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726185AbgIXVl3 (ORCPT ); Thu, 24 Sep 2020 17:41:29 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72B73C0613CE for ; Thu, 24 Sep 2020 14:41:29 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1600983687; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PH7EM+jC9sAvN+hNyU7Ecq4szctd2TEmbXpjLXpwHLk=; b=s9aB8dgH+LEJxttQJWGE11+AGwucCe4uEwpFHGxM5Il9nb81ncN7r8Hx+3OJ4kNyYgM9dO kDfcog9G7Ae/sxkBpu4vLApMbwWN5le+lk70lojuOGsLJL9W9c6CKNvdQeBi3D7xvEu3cQ FOU6VlOqEjjJ5knJS9TSLoCP2sg04q4KZmCPxRcRB/WFQb8j9hv6/jKLOJw0xJ8dXflnix X4/ncxiUBavxFpN/gfRiblq6Sk192R/KgwTsfJX7aKtPEOTLzvHHMMr2igcXsG8uge6sN0 byXLKaFRd6o/zeeXaTJuGR7U5fRMTbVuR4LHKBHGLiXrhaCRWJQQiu7ZdRW4rQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1600983687; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PH7EM+jC9sAvN+hNyU7Ecq4szctd2TEmbXpjLXpwHLk=; b=vCvDhw1zpzFDJBuOG8UL0KkN9R1JI3ss+WSRGs73GkIopLFT6yj1AwBS6aQnWh9Fqt8jHQ pkn9QBcJV5uqC/CQ== To: Walter Wu , Andrew Morton , John Stultz , Stephen Boyd , Marco Elver , Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Andrey Konovalov , Matthias Brugger Cc: kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, wsd_upstream , linux-mediatek@lists.infradead.org, Walter Wu Subject: Re: [PATCH v4 1/6] timer: kasan: record timer stack In-Reply-To: <20200924040335.30934-1-walter-zh.wu@mediatek.com> References: <20200924040335.30934-1-walter-zh.wu@mediatek.com> Date: Thu, 24 Sep 2020 23:41:27 +0200 Message-ID: <87h7rm97js.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 24 2020 at 12:03, Walter Wu wrote: > When analyze use-after-free or double-free issue, recording the timer > stacks is helpful to preserve usage history which potentially gives > a hint about the affected code. > > Record the most recent two timer init calls in KASAN which are printed > on failure in the KASAN report. > > For timers it has turned out to be useful to record the stack trace > of the timer init call. In which way? And what kind of bug does it catch which cannot be catched by existing debug mechanisms already? > Because if the UAF root cause is in timer init, then user can see > KASAN report to get where it is registered and find out the root > cause. What? If the UAF root cause is in timer init, then registering it after using it in that very same function is pretty pointless. > It don't need to enable DEBUG_OBJECTS_TIMERS, but they have a chance > to find out the root cause. There is a lot of handwaving how useful this is, but TBH I don't see the value at all. DEBUG_OBJECTS_TIMERS does a lot more than crashing on UAF. If KASAN provides additional value over DEBUG_OBJECTS_TIMERS then spell it out, but just saying that you don't need to enable DEBUG_OBJECTS_TIMERS is not making an argument for that change. Try again please. Thanks, tglx