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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,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 EF212C2BA19 for ; Mon, 13 Apr 2020 14:19:54 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 96DD720776 for ; Mon, 13 Apr 2020 14:19:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZsTY/jfA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96DD720776 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 4B99D8E011C; Mon, 13 Apr 2020 10:19:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 468AC8E0104; Mon, 13 Apr 2020 10:19:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3571E8E011C; Mon, 13 Apr 2020 10:19:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0145.hostedemail.com [216.40.44.145]) by kanga.kvack.org (Postfix) with ESMTP id 1A5358E0104 for ; Mon, 13 Apr 2020 10:19:54 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D344F4DAC for ; Mon, 13 Apr 2020 14:19:53 +0000 (UTC) X-FDA: 76703040666.15.kick51_565d78f9f2113 X-HE-Tag: kick51_565d78f9f2113 X-Filterd-Recvd-Size: 6654 Received: from mail-wm1-f68.google.com (mail-wm1-f68.google.com [209.85.128.68]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Mon, 13 Apr 2020 14:19:53 +0000 (UTC) Received: by mail-wm1-f68.google.com with SMTP id x4so9467477wmj.1 for ; Mon, 13 Apr 2020 07:19:53 -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=1SRhX73i1rxKCDlEZFqcD1e5E/+V2TwOGzqoCEBrZDQ=; b=ZsTY/jfAi7uPrcEtKnWGBmGTM5QjjR7Q7pzTY00k45VBoIY0OlfWYDVbst7/2po18b sdbCgad1WD1TKlnTuE6RRC9iZvnBIl5KrL/xB22newdD9ma/C6Mkg40XgK+I68v2bX1X 5gT0547SBgvpXLOM0aeFspuziCkYolSd9S5eOsg5psRdfAbBg/TUMVQjCI/TVfEnue9y uzLg5PiN1ilGDkzn8LMVB4sYgGcLV+Z51EWFW2drEyURLqXUlvyAxOYjKIIBZY0CLHfh yq8juGHjJ13/MUyhRS1A8LDBqIR8ar23q/P6XoEDHDtTSIhPSaW8tj1zKabNOtMoEwqT lYBA== 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=1SRhX73i1rxKCDlEZFqcD1e5E/+V2TwOGzqoCEBrZDQ=; b=HCKA/SeNvp66xQtOduqQtbr6A50uTSnpiJdCSh3bhl6OrG1KcupoJPSh9wZaxBkwOu c5ly3+IW4+hWtNmnwLiGcH5wyXGOQL59axy5VlrtQFrKlG+OjGahXmk51aXxkfY2GFO7 qxeEdLyovNTnQDfKQUNmkMeHPWi7wzpSJNfZA2eKfIU4rFqIHWf93f5MItgY8fCRobXb uuKdQh47fOEbG9M/slSIT8UesihE6ATHzVUxJxQhZLIPA5fRb5EEdjwt1eiipBegL5kO O3RQplTHVdXSOh2OAn+dEH8uSPuGICr3l3tNWfDZMhcN8Cwd/7QLV8Fkg8c+2A7QNrtr WHWg== X-Gm-Message-State: AGi0PuY65/w2g5VaUaWsPGJ7D0f8qVJBd1RKvYHht5GowODTKCNWUArE VVBKBNRPCHeVaQRUimKKFSmLAN9xPo73DsSAcME6Bw== X-Google-Smtp-Source: APiQypJH8w9l03li7Gt1pC29WYRQXEkU13LH0DFZvOFHQtfOPbc//GXUkydi9Wqr4paiOSMYamKnsAH8AR4gCdLvGqY= X-Received: by 2002:a1c:ed1a:: with SMTP id l26mr18765149wmh.175.1586787591869; Mon, 13 Apr 2020 07:19:51 -0700 (PDT) MIME-Version: 1.0 References: <20200325161249.55095-1-glider@google.com> <20200325161249.55095-33-glider@google.com> In-Reply-To: From: Alexander Potapenko Date: Mon, 13 Apr 2020 16:19:40 +0200 Message-ID: Subject: Re: [PATCH v5 32/38] kmsan: disable strscpy() optimization under KMSAN To: Andrey Konovalov Cc: Vegard Nossum , Dmitry Vyukov , Marco Elver , Linux Memory Management List , Alexander Viro , Andreas Dilger , Andrew Morton , 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 Hocko , 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 Wed, Apr 8, 2020 at 6:01 PM Andrey Konovalov wro= te: > > On Wed, Mar 25, 2020 at 5:14 PM wrote: > > > > Disable the efficient 8-byte reading under KMSAN to avoid false positiv= es. > > Another user of read_word_at_a_time() is dentry_string_cmp() in > dcache.c, should we disable it there as well? > I think we'd better disable DCACHE_WORD_ACCESS if KMSAN is enabled. Will do that in v6. > > > > Signed-off-by: Alexander Potapenko > > To: Alexander Potapenko > > Cc: Vegard Nossum > > Cc: Dmitry Vyukov > > Cc: Marco Elver > > Cc: Andrey Konovalov > > Cc: linux-mm@kvack.org > > > > --- > > > > v4: > > - actually disable the optimization under KMSAN via max=3D0 > > - use IS_ENABLED as requested by Marco Elver > > > > Change-Id: I25d1acf5c3df6eff85894cd94f5ddbe93308271c > > --- > > lib/string.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/lib/string.c b/lib/string.c > > index 6012c385fb314..fec929e70f1a5 100644 > > --- a/lib/string.c > > +++ b/lib/string.c > > @@ -202,6 +202,14 @@ ssize_t strscpy(char *dest, const char *src, size_= t count) > > max =3D 0; > > #endif > > > > + /* > > + * read_word_at_a_time() below may read uninitialized bytes aft= er the > > + * trailing zero and use them in comparisons. Disable this opti= mization > > + * under KMSAN to prevent false positive reports. > > + */ > > + if (IS_ENABLED(CONFIG_KMSAN)) > > + max =3D 0; > > + > > while (max >=3D sizeof(unsigned long)) { > > unsigned long c, data; > > > > -- > > 2.25.1.696.g5e7596f4ac-goog > > --=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