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=-13.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 5E72BC43603 for ; Thu, 5 Dec 2019 10:31:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E83D24654 for ; Thu, 5 Dec 2019 10:31:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eYZMat2H" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729018AbfLEKbk (ORCPT ); Thu, 5 Dec 2019 05:31:40 -0500 Received: from mail-qv1-f67.google.com ([209.85.219.67]:37503 "EHLO mail-qv1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728794AbfLEKbk (ORCPT ); Thu, 5 Dec 2019 05:31:40 -0500 Received: by mail-qv1-f67.google.com with SMTP id t7so1081554qve.4 for ; Thu, 05 Dec 2019 02:31:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=AIwfFBjY5pjo/AwQlYLo1XDjqkJbAe8kAMyvBg+3yAM=; b=eYZMat2HE3FLjyOA43FqB/w1GkyQ6frF+j0XPKrIc1es0ljwtwwex1ueuRIGRIMTBZ uD+v4Pu8j72Kr9PWzQSPmIJG+vAutrUoXY/DlvJLqYzq5Mb/MQS4MLbL7d8bKQHe1CLm /obGnlsvGr3IPK2Vijtfo13yPAeYuZFUYqQkYHaAeMoqlrCkVVKjcDjzVsYKs3oi/E8k b+AnNdv8b+VIdUWVko0227dY1YSR3tuiDGqWP2ttdlmRuhCA6DLLr4suNNTt1QEYRlE9 nBUheeQUAyU8L/9eU7qRmuCPsDRs7GTa8MiaTjkR0yLps1RW1cvnWRVFxTxEORtDL2EI xkcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=AIwfFBjY5pjo/AwQlYLo1XDjqkJbAe8kAMyvBg+3yAM=; b=V/tiGLpkadhkzSLzlj6J2DYD2DHbJAHQYKFze4VrGqvnt56mggkYvlQV/+OmjoFN8w gVEojmTHYkBDJt09b0O77LZtEy+iJgL9ipAXUR0vTXuCCYhRRvJSVf+4uKeOoKmEosFG P1085y+D4UbtJ+4S9E1W8plvp6Ece0V0Rhz9Onm/fLZYXz+JTTLSdbptmVnspc3WcHdX Hpj6eBEeWu8N6FaO5HNeUbFvDZnlqbS22pL0RdF6fWY08r0nDUpeeP1sWHUKPSrecwx7 E2nimKxF7JsPg+JlPg33nuQaFRwsd+3y5YcuY/mTwnGwgFzPAlF/eHgCWRhaaVcn7liw I+2A== X-Gm-Message-State: APjAAAWxhyNxx+SeSa6FNbfhWzWYmLuT2yt0tMM6TSYQ1MEe14tvYnFW uDYBGm/RpNi/BITbyzBsA0UiaE2zH1hUsobacv6X4w== X-Google-Smtp-Source: APXvYqzUwvRfklGx7jn2Qx5E8Ckootk5Q7YtZLTMNHA7rrZOeakEoQMPUMd3z45mweABnO/Dvphg9v6UIqE2DS3Vf+k= X-Received: by 2002:a0c:f8d1:: with SMTP id h17mr6889518qvo.80.1575541898628; Thu, 05 Dec 2019 02:31:38 -0800 (PST) MIME-Version: 1.0 References: <0000000000003e640e0598e7abc3@google.com> <41c082f5-5d22-d398-3bdd-3f4bf69d7ea3@redhat.com> In-Reply-To: From: Dmitry Vyukov Date: Thu, 5 Dec 2019 11:31:27 +0100 Message-ID: Subject: Re: KASAN: slab-out-of-bounds Read in fbcon_get_font To: Paolo Bonzini Cc: syzbot , Andrey Ryabinin , Bartlomiej Zolnierkiewicz , Daniel Thompson , Daniel Vetter , DRI , ghalat@redhat.com, Gleb Natapov , gwshan@linux.vnet.ibm.com, "H. Peter Anvin" , James Morris , kasan-dev , KVM list , Linux Fbdev development list , LKML , linux-security-module , Maarten Lankhorst , Ingo Molnar , Michael Ellerman , Tetsuo Handa , Russell Currey , Sam Ravnborg , "Serge E. Hallyn" , stewart@linux.vnet.ibm.com, syzkaller-bugs , Kentaro Takeda , Thomas Gleixner , "the arch/x86 maintainers" Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Thu, Dec 5, 2019 at 11:22 AM Paolo Bonzini wrote: > > On 05/12/19 11:16, Dmitry Vyukov wrote: > > On Thu, Dec 5, 2019 at 11:13 AM Paolo Bonzini wrote: > >> > >> On 04/12/19 22:41, syzbot wrote: > >>> syzbot has bisected this bug to: > >>> > >>> commit 2de50e9674fc4ca3c6174b04477f69eb26b4ee31 > >>> Author: Russell Currey > >>> Date: Mon Feb 8 04:08:20 2016 +0000 > >>> > >>> powerpc/powernv: Remove support for p5ioc2 > >>> > >>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=127a042ae00000 > >>> start commit: 76bb8b05 Merge tag 'kbuild-v5.5' of > >>> git://git.kernel.org/p.. > >>> git tree: upstream > >>> final crash: https://syzkaller.appspot.com/x/report.txt?x=117a042ae00000 > >>> console output: https://syzkaller.appspot.com/x/log.txt?x=167a042ae00000 > >>> kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b > >>> dashboard link: > >>> https://syzkaller.appspot.com/bug?extid=4455ca3b3291de891abc > >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11181edae00000 > >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105cbb7ae00000 > >>> > >>> Reported-by: syzbot+4455ca3b3291de891abc@syzkaller.appspotmail.com > >>> Fixes: 2de50e9674fc ("powerpc/powernv: Remove support for p5ioc2") > >>> > >>> For information about bisection process see: > >>> https://goo.gl/tpsmEJ#bisection > >>> > >> > >> Why is everybody being CC'd, even if the bug has nothing to do with the > >> person's subsystem? > > > > The To list should be intersection of 2 groups of emails: result of > > get_maintainers.pl on the file identified as culprit in the crash > > message + emails extracted from the bisected to commit. > > Ah, and because the machine is a KVM guest, kvm_wait appears in a lot of > backtrace and I get to share syzkaller's joy every time. :) I don't see any mention of "kvm" in the crash report. And it's only 1 file, not all of them, in this case I would expect it to be drivers/video/fbdev/core/fbcon.c. So it should be something different. > This bisect result is bogus, though Tetsuo found the bug anyway. > Perhaps you can exclude commits that only touch architectures other than > x86? We do this. It work sometimes. But sometimes it hits non-deterministic kernel build bugs: https://github.com/google/syzkaller/issues/1271#issuecomment-559093018 And in this case it hit some git bisect weirdness which I can't explain yet: https://github.com/google/syzkaller/issues/1527