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=-19.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,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 49718C432C0 for ; Tue, 3 Dec 2019 11:19:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F147C206EC for ; Tue, 3 Dec 2019 11:19:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="RBNUNbB+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F147C206EC Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A3A166B04A6; Tue, 3 Dec 2019 06:19:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9EB906B04A7; Tue, 3 Dec 2019 06:19:30 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9005B6B04A8; Tue, 3 Dec 2019 06:19:30 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0132.hostedemail.com [216.40.44.132]) by kanga.kvack.org (Postfix) with ESMTP id 7966F6B04A6 for ; Tue, 3 Dec 2019 06:19:30 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 3C172180AD817 for ; Tue, 3 Dec 2019 11:19:30 +0000 (UTC) X-FDA: 76223584500.06.bomb38_8d1296d323114 X-HE-Tag: bomb38_8d1296d323114 X-Filterd-Recvd-Size: 7524 Received: from mail-wr1-f67.google.com (mail-wr1-f67.google.com [209.85.221.67]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Tue, 3 Dec 2019 11:19:29 +0000 (UTC) Received: by mail-wr1-f67.google.com with SMTP id b6so3251978wrq.0 for ; Tue, 03 Dec 2019 03:19:29 -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:content-transfer-encoding; bh=3Td2V8feE9NzMb0mFt7teDPI2RUKEYwUfW3hHRignas=; b=RBNUNbB+n5qzJvFJDK0n211MzNYxgIHxGjSRGVU+bec7vORdu/5TogCf9UyNdmmfz8 qOwQmuGskY+nEIdqqBI4EsY0/jQoVRtoukJ25SoPxvBfyoWRrcYQWau9D2lb81Oy7Ffh pN8xZS1KTLZEtR+caWu/Z4A4EcktoRnpQfNixGKAqahzBU/3rMWLAksIvk5l5cMAWuf4 XUXPViimlvrZThTdCFMEZgtYa719UVMyjCjsNw0d6FEdtuKTVJ5SlTLto56fXbaN3Isj /bk9nkP0robimVMXQEWOgZOMOO8j4tj4Ewvc8Nt4idEEEukhk6hYog2++fNy5/HBeObF yOIQ== 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=3Td2V8feE9NzMb0mFt7teDPI2RUKEYwUfW3hHRignas=; b=fHv6/3xjoDA5nw0ILrCr2ZADRgbnLddvx72adv9GAsTIqqvcQXcMveNfajGkxXcjMI V9Yv7LoOzXTOcH3KPRfv7GwPnZ0vwguZnpwi0l+LvIwwGs4yjBaMslWAkYAUyup4MLt+ 7ev1pChCUfpmyGNTPyMESzwOC1LKMa/XjFbmfOSHvyLQcnz/tFFIBI0VI6U5eKkWphu8 sG0vkFjGsSwWpOuojIAOGkOTnZPB5+lI8wx+RDgPp7VRjVQzYWxJJeplqIbGkGf8hjiS wFixhHUPtEwWg8TJEDzCq0YwfjEvTEhSJYXc1MYD3okMMTmyuNdwZDSRRHu57QpY4MSs F3ng== X-Gm-Message-State: APjAAAVfF0k/3bVUj37JoLw1lAjDHm6xzZ29c8GjPOazzr5DZT1SxvpS i/d5ah6bFdDIYQk+WK6wdhl3qBf8JstB6zYpCPpfhQ== X-Google-Smtp-Source: APXvYqx3+2066up3cJW02cwwQHw1G+n61rK0m5mjRhZLFbgjffMdv8Z9seIFjS0gCKWI0PyhMvUBIV7DiO/vThMZlGw= X-Received: by 2002:adf:e2cd:: with SMTP id d13mr4563954wrj.221.1575371967758; Tue, 03 Dec 2019 03:19:27 -0800 (PST) MIME-Version: 1.0 References: <20191122112621.204798-1-glider@google.com> <20191122112621.204798-32-glider@google.com> In-Reply-To: From: Alexander Potapenko Date: Tue, 3 Dec 2019 12:19:16 +0100 Message-ID: Subject: Re: [PATCH RFC v3 31/36] kmsan: disable strscpy() optimization under KMSAN To: Marco Elver Cc: Vegard Nossum , Dmitry Vyukov , Linux Memory Management List , Al Viro , Andreas Dilger , Andrew Morton , Andrey Konovalov , Andrey Ryabinin , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Christoph Hellwig , Christoph Hellwig , "Darrick J. Wong" , "David S. Miller" , Dmitry Torokhov , Eric Biggers , Eric Dumazet , Eric Van Hensbergen , Greg Kroah-Hartman , Harry Wentland , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jason Wang , Jens Axboe , Marek Szyprowski , Mark Rutland , "Martin K. Petersen" , Martin Schwidefsky , Matthew Wilcox , "Michael S. Tsirkin" , Michal Simek , Petr Mladek , Qian Cai , Randy Dunlap , Robin Murphy , Sergey Senozhatsky , Steven Rostedt , Takashi Iwai , "Theodore Ts'o" , Thomas Gleixner , Vasily Gorbik , Wolfram Sang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Dec 2, 2019 at 5:23 PM Alexander Potapenko wrot= e: > > On Mon, Dec 2, 2019 at 4:51 PM Marco Elver wrote: > > > > On Fri, 22 Nov 2019 at 12:28, wrote: > > > > > > Disable the efficient 8-byte reading under KMSAN to avoid false posit= ives. > > > > > > Signed-off-by: Alexander Potapenko > > > To: Alexander Potapenko > > > Cc: Vegard Nossum > > > Cc: Dmitry Vyukov > > > Cc: linux-mm@kvack.org > > > > > > --- > > > > > > Change-Id: I25d1acf5c3df6eff85894cd94f5ddbe93308271c > > > --- > > > lib/string.c | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/lib/string.c b/lib/string.c > > > index 08ec58cc673b..15efdc51bda6 100644 > > > --- a/lib/string.c > > > +++ b/lib/string.c > > > @@ -186,7 +186,10 @@ ssize_t strscpy(char *dest, const char *src, siz= e_t count) > > > if (count =3D=3D 0 || WARN_ON_ONCE(count > INT_MAX)) > > > return -E2BIG; > > > > > > -#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > > > +/** > > > > Why a doc comment? > Will fix, thanks! > > > + * Disable the efficient 8-byte reading under KMSAN to avoid false p= ositives. > > > + */ > > > > AFAIK the CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS case is about > > unaligned accesses crossing page boundaries. In the #else case it's > > still going to do word-at-a-time if both src and dest are aligned, so > > the comment above is somewhat inaccurate. > Yes, this makes little sense. > Reading word-at-a-time shouldn't induce any errors, although it may > generate redundant stack IDs for values that will never be used. > I'll try to drop this patch. Turns out the patch is still needed, as read_word_at_a_time may read uninitialized bytes which are then used in comparisons. I've changed the patch to always set max=3D0 under KMSAN: https://github.com/google/kmsan/commit/3ff43863bf53dd871a3d4dc4fbb2a76d79b4= db4f Will include this version in v4 series. > > > > +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && !defined(CONF= IG_KMSAN) > > > /* > > > * If src is unaligned, don't cross a page boundary, > > > * since we don't know if the next page is mapped. > > > -- > > > 2.24.0.432.g9d3f5f5b63-goog > > > > > > > -- > 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 --=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