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 1341DC2D0EA for ; Wed, 8 Apr 2020 16:01:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BCBE12082F for ; Wed, 8 Apr 2020 16:01:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="pGGJ6jVz" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BCBE12082F 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 648EF8E000D; Wed, 8 Apr 2020 12:01:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5AEB48E0006; Wed, 8 Apr 2020 12:01:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 474D38E000D; Wed, 8 Apr 2020 12:01:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0111.hostedemail.com [216.40.44.111]) by kanga.kvack.org (Postfix) with ESMTP id 2A96F8E0006 for ; Wed, 8 Apr 2020 12:01:01 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id E0D6499AC for ; Wed, 8 Apr 2020 16:01:00 +0000 (UTC) X-FDA: 76685151480.07.iron09_6018d8581ac17 X-HE-Tag: iron09_6018d8581ac17 X-Filterd-Recvd-Size: 5896 Received: from mail-pj1-f68.google.com (mail-pj1-f68.google.com [209.85.216.68]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Wed, 8 Apr 2020 16:01:00 +0000 (UTC) Received: by mail-pj1-f68.google.com with SMTP id kx8so11459pjb.5 for ; Wed, 08 Apr 2020 09:01:00 -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; bh=+7QO/Ns9YrBM2Hn2tcpEIiBCCXBmqHN1YD1bUicBXE4=; b=pGGJ6jVzMHkg03/cqUgmUnhYuDfpO8VKaDrWpZmLqImUo2TZjbqYkgX/SDLZe0EnWS wVxkJ4yAec/f3LVbj9hyCs7IIoLPOtSS/Kpdhswzh7EMV014ahvTiTeuJXt1q2v6RBoB oW0tGG+2x2zU4CB7DIaYQZe1KKEcb/mfba1OKUlkKJa4EwVNEtmK/lVziArTdpsjyP9P kfZctd2cGHKlUNUdD/iVzoVkHVa50QXzjjvyko9N1VLnJ7Z3Bb8vvbZ1P+P3uH4Md7Li DDxhXvdcIB1MGfr5otaQsVDHeOYfryrBPYgQdR6BQgSFy8odBWi53Y+PogoPn0LRKgpr MOFA== 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=+7QO/Ns9YrBM2Hn2tcpEIiBCCXBmqHN1YD1bUicBXE4=; b=H0Ok19/eoPxNQsUzeiayOYsGFirJfrs1nb97cGD0rZc6yAm19wOYJGShV3QO/WkmWu fyn6O+zw9S+HOAw6w1apW8JOTseM7mNDkKAY9oIHizUq5IKgF4A9jg+RD7ANpp+QR30I 2WZkYoITNSvC28sN3kzsKHC6PTaCyyUGDomLyQDor2cTYZBzUlgvOBThCeIYl4rOKJxH BQs+KwP9ADtxLQTVPWpGwlHLa/fNP1zwZMYHIWS9q1o/2UpBZd340oEYQLD97Jbk6VkX w667j+E8oWc9s2FJiND7uoWI3bwd/wAHtqlT0obTnKlTR5N02anxRh5VYN7D3UjQbhEl EGDQ== X-Gm-Message-State: AGi0PuacTtv5eMF3OZJhKyajqvtP4Ne6Mw9I5jrLWTHgVWzg3m+4kz03 TbQFFEePm18mQAVJCzFP6ENjOY1liKrBcy5x6e9vGg== X-Google-Smtp-Source: APiQypLQsGL/MF3ALPSeKk2/u3Z9qESNqfpxe52v5lqUIwnhat9uorws4oH/xxIR1Mi5W/8mRBX0pADZXpZRiE4RaYY= X-Received: by 2002:a17:90b:1985:: with SMTP id mv5mr6297310pjb.69.1586361658777; Wed, 08 Apr 2020 09:00:58 -0700 (PDT) MIME-Version: 1.0 References: <20200325161249.55095-1-glider@google.com> <20200325161249.55095-33-glider@google.com> In-Reply-To: <20200325161249.55095-33-glider@google.com> From: Andrey Konovalov Date: Wed, 8 Apr 2020 18:00:47 +0200 Message-ID: Subject: Re: [PATCH v5 32/38] kmsan: disable strscpy() optimization under KMSAN To: Alexander Potapenko 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" 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, Mar 25, 2020 at 5:14 PM wrote: > > Disable the efficient 8-byte reading under KMSAN to avoid false positives. Another user of read_word_at_a_time() is dentry_string_cmp() in dcache.c, should we disable it there as well? > > 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=0 > - 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 = 0; > #endif > > + /* > + * read_word_at_a_time() below may read uninitialized bytes after the > + * trailing zero and use them in comparisons. Disable this optimization > + * under KMSAN to prevent false positive reports. > + */ > + if (IS_ENABLED(CONFIG_KMSAN)) > + max = 0; > + > while (max >= sizeof(unsigned long)) { > unsigned long c, data; > > -- > 2.25.1.696.g5e7596f4ac-goog >