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_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 4B88AC10F27 for ; Mon, 9 Mar 2020 11:53:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1A51C2051A for ; Mon, 9 Mar 2020 11:53:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="oaL3YTt4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726415AbgCILxl (ORCPT ); Mon, 9 Mar 2020 07:53:41 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:38355 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726248AbgCILxl (ORCPT ); Mon, 9 Mar 2020 07:53:41 -0400 Received: by mail-wm1-f68.google.com with SMTP id n2so2765229wmc.3 for ; Mon, 09 Mar 2020 04:53:40 -0700 (PDT) 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:content-transfer-encoding; bh=A+8e1ZJvLxFvMv1z1RgLvbeZ9xImIdjD3uf9/zDP4HQ=; b=oaL3YTt4xI7Y5XHj5qLl3V2HPwybW5fnx9ISn59T54mho8oRaOdecnADmdEO/5MlED n/eiDObVT6osUEtWowhpIsOonWANHc0ZuaxiHl/Pbo42elEUr0uOiZe0EX7qVqnHlffo wvnX687QUdArrst4oIkJMG4TEnjlV/cvlpuoXf8VRw2ADfSo9VBAkPvfHNWOWDWQmL4P axyqJ4FWW3/UIjwHQEh6j4Qh90PQfmz7JOXBygX2tDuhWy7bDwISA5Spir104SpXybPG ZXC/seO2SuwdS9pTlPODArs+7mHWzXNE4aatJJN50QxS4as9RmUyho6hu0Auusuu8g+s KGpQ== 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:content-transfer-encoding; bh=A+8e1ZJvLxFvMv1z1RgLvbeZ9xImIdjD3uf9/zDP4HQ=; b=fdCswcoPRQehUUi4sYbDfgO7/STVBAdYyNkRe5xnkPbKMCm1Jup6D3qRpOnUV0ARf/ OatqWk7aW3Z4zoyKc9FC9pYx+qHZE3+jXcifTm5oqeAFoKJB2C0oEzEYUmJZJ4X0mZJb ThmDJAudKgHVyGmD99MKxma4QTK+RdSAsndxkhtdE4cPJ86GVYeq4+8PRRFWoNx/A0pF Sk8B3msmW1+n0P1J3Kq5FoymQG2/512uZ/i2HaUGTKJFWUIkV4KYs+H3+2IwXPLoHHHi ERjtkjYJ0w8a6N3gpLS6syCS2vHgZML+bVDlXMYOBSWESXkjo5IlATuK+no95MQe6/q3 BArw== X-Gm-Message-State: ANhLgQ3Y1Ope39b56fDutsw6DhmE5Bo2eEWaaHAh8D9ZaF5WjIjwou74 p5UOT5W1xMHvLTUQ3ClkZaJQYSux/7jKbuD+MalfvZQj1l8= X-Google-Smtp-Source: ADFU+vsvzlW7OSvkTeLOzgfo58rs5LGHa8FxbgTgp+IGRG22sPK0JWBxQHkRb8/ZvjA/96kJZL/SSEMlEcv3yr6IoXA= X-Received: by 2002:a1c:9a41:: with SMTP id c62mr85973wme.37.1583754819857; Mon, 09 Mar 2020 04:53:39 -0700 (PDT) MIME-Version: 1.0 References: <000000000000938a57059f7cafe4@google.com> <20200307235437.GW15444@sol.localdomain> <20200308032434.GX15444@sol.localdomain> In-Reply-To: <20200308032434.GX15444@sol.localdomain> From: Alexander Potapenko Date: Mon, 9 Mar 2020 12:53:28 +0100 Message-ID: Subject: Re: KMSAN: uninit-value in snapshot_compat_ioctl To: Eric Biggers Cc: syzbot , len.brown@intel.com, LKML , Linux PM , Pavel Machek , "Rafael J. Wysocki" , syzkaller-bugs Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org > > Looks like a KMSAN false positive? As far as I can tell, the memory is= being > > initialized by put_user() called under set_fs(KERNEL_DS). Why? put_user() doesn't write to kernel memory, instead it copies a value to the userspace. That's why KMSAN performs kmsan_check_memory() on it. It would actually be better if KMSAN printed an kernel-infoleak warning ins= tead. > Although, it also looks like the problematic code can just be removed, si= nce > always sizeof(compat_loff_t) =3D=3D sizeof(loff_t). I'll send a patch to= do that... Thanks! --=20 Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Stra=C3=9Fe, 33 80636 M=C3=BCnchen Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg