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=-13.6 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_PASS,URIBL_BLOCKED,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 2AD35C43387 for ; Fri, 4 Jan 2019 08:58:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED7D721871 for ; Fri, 4 Jan 2019 08:58:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="vuKrCxhZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727361AbfADI6I (ORCPT ); Fri, 4 Jan 2019 03:58:08 -0500 Received: from mail-it1-f194.google.com ([209.85.166.194]:38189 "EHLO mail-it1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726817AbfADI6H (ORCPT ); Fri, 4 Jan 2019 03:58:07 -0500 Received: by mail-it1-f194.google.com with SMTP id h65so717938ith.3 for ; Fri, 04 Jan 2019 00:58:06 -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=20usoIc4RkJRiBEBTyYQHbq1Jt7l3TB1S1E8Xf7YN58=; b=vuKrCxhZqA5l7H5Wi+/TUYqUIT95OSOWtAWoBrvDLvSO5SI5x3x/eBuYd9vJhnCLs/ EUp3sByD67cqNh7z/YYEaPeuxexh+JQ2jscIS75yDSM08A5aeNnrnL4kO/5uGDv11haY pAWFl2sPWBkVjK8Ftz44xGAZThIt7RjzNB7JuHzRe+zs61hdpVJPsUt3Ms00gGJ032aO kUmzuoo6i3tFqR6blir6YsOEk7oO0Oy4xjc5en/u/vdanYrYLW4sik/8tL4Xkszq4biU b+AYUB+2W5VV0Qy3TFbfHt0STnZi+CnpuaLWJ6RpJ3rKTxFl+1qv+K/AgXxg6vx6uR1+ FpIw== 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=20usoIc4RkJRiBEBTyYQHbq1Jt7l3TB1S1E8Xf7YN58=; b=nu3JI9Lbx1AbV/hmp+8U8fqCibwdP74RoXGxKNQskuW48pCKM++6FhA+Rjq1apfpHw 01q4weULwkUVBc72bjTYZQ5TPk3E6TeM1ukbeJ4cfNkWt+A1MJT6bWK7282AWlWadvJl bVPVgqsDEI8mXnJ7gnqePtN1aUnjFtQUI4Jk5tuWGo8BtVmxGQv1ulqMmdjvYE8OtCDe 9GcDIYxLKsGLL3jpf8DqHS8+64riPmQe9eT51jo9E0kYccKm91owCFH3QFekGq5R/Lc4 f+RVxhhlpQdCBxkTGNwa95+DcYBiG3MjwdgqJfL2Ah4NIvk2QDp3T3hhimZe4e4+YyWS Yomg== X-Gm-Message-State: AJcUukds/5BcqOrX6NamUJ+QlSGdmLCSdqlCqclLFLV/JKO8Hb1R7a9F Yw1DMl8EODD3jPI2MvaE2Ejh4DJGnmHf4J+Pjv69Gg== X-Google-Smtp-Source: ALg8bN6Cy6jiOwdeoPsYLCKaE7+c5pzwCJpP999/XZx+O44Ih0ik7j+lZ+wuGIz97quRKepGhThWGzgD+Ezw/aqeyO8= X-Received: by 2002:a05:660c:f94:: with SMTP id x20mr406231itl.144.1546592285557; Fri, 04 Jan 2019 00:58:05 -0800 (PST) MIME-Version: 1.0 References: <000000000000c06550057e4cac7c@google.com> <52835ef5-6351-3852-d4ba-b6de285f96f5@suse.cz> In-Reply-To: <52835ef5-6351-3852-d4ba-b6de285f96f5@suse.cz> From: Dmitry Vyukov Date: Fri, 4 Jan 2019 09:57:54 +0100 Message-ID: Subject: Re: KMSAN: uninit-value in mpol_rebind_mm To: Vlastimil Babka Cc: syzbot , Andrea Arcangeli , Andrew Morton , Alexander Potapenko , "Kirill A. Shutemov" , LKML , Linux-MM , linux@dominikbrodowski.net, Michal Hocko , David Rientjes , syzkaller-bugs , xieyisheng1@huawei.com, zhong jiang 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 Fri, Jan 4, 2019 at 9:50 AM Vlastimil Babka wrote: > > On 1/3/19 9:42 AM, Dmitry Vyukov wrote: > > On Thu, Jan 3, 2019 at 9:36 AM Vlastimil Babka wrote: > >> > >> > >> On 12/31/18 8:51 AM, syzbot wrote: > >>> Hello, > >>> > >>> syzbot found the following crash on: > >>> > >>> HEAD commit: 79fc24ff6184 kmsan: highmem: use kmsan_clear_page() in cop.. > >>> git tree: kmsan > >>> console output: https://syzkaller.appspot.com/x/log.txt?x=13c48b67400000 > >>> kernel config: https://syzkaller.appspot.com/x/.config?x=901dd030b2cc57e7 > >>> dashboard link: https://syzkaller.appspot.com/bug?extid=b19c2dc2c990ea657a71 > >>> compiler: clang version 8.0.0 (trunk 349734) > >>> > >>> Unfortunately, I don't have any reproducer for this crash yet. > >>> > >>> IMPORTANT: if you fix the bug, please add the following tag to the commit: > >>> Reported-by: syzbot+b19c2dc2c990ea657a71@syzkaller.appspotmail.com > >>> > >>> ================================================================== > >>> BUG: KMSAN: uninit-value in mpol_rebind_policy mm/mempolicy.c:353 [inline] > >>> BUG: KMSAN: uninit-value in mpol_rebind_mm+0x249/0x370 mm/mempolicy.c:384 > >> > >> The report doesn't seem to indicate where the uninit value resides in > >> the mempolicy object. > > > > Yes, it doesn't and it's not trivial to do. The tool reports uses of > > unint _values_. Values don't necessary reside in memory. It can be a > > register, that come from another register that was calculated as a sum > > of two other values, which may come from a function argument, etc. > > I see. BTW, the patch I sent will be picked up for testing, or does it > have to be in mmotm/linux-next first? It needs to be in upstream tree. Since KMSAN is not upstream, we have only 1 branch that is based on upstream and is periodically rebased: https://github.com/google/kmsan If the bug would have a repro, then we could ask syzbot to test this patch on top of KMSAN tree. But unfortunately it doesn't.