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 E988DC432C0 for ; Mon, 2 Dec 2019 15:37:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8712520881 for ; Mon, 2 Dec 2019 15:37:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CYyWpV6c" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8712520881 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 018F86B0007; Mon, 2 Dec 2019 10:37:06 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EE5736B0008; Mon, 2 Dec 2019 10:37:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DADF96B000A; Mon, 2 Dec 2019 10:37:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0163.hostedemail.com [216.40.44.163]) by kanga.kvack.org (Postfix) with ESMTP id C14F66B0007 for ; Mon, 2 Dec 2019 10:37:05 -0500 (EST) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 8193552BF for ; Mon, 2 Dec 2019 15:37:05 +0000 (UTC) X-FDA: 76220604810.11.band18_3a200396e045 X-HE-Tag: band18_3a200396e045 X-Filterd-Recvd-Size: 6499 Received: from mail-vs1-f68.google.com (mail-vs1-f68.google.com [209.85.217.68]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Mon, 2 Dec 2019 15:37:04 +0000 (UTC) Received: by mail-vs1-f68.google.com with SMTP id l24so66233vsr.12 for ; Mon, 02 Dec 2019 07:37:04 -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=r4gVEI/WwJsRjZDTqv+oTWXfcuwUi/UjDVhVXwXhWOE=; b=CYyWpV6cTxXwRbRDcKPLPiakuOmp9ywJkeM3rkpbc7AermIeRDcYyxTVNgoR6OOOWo xRUUmZOk5FsjZ8Va186GMld/ZcDB7CLp0nJ6U9D4RKQycMTvnVet+L6qHIY2H2l5JKZd l20y0o1Z2jhkoCu3B8XHwe2bltE+Oaz8gQs7BgJOso8HrFpSBtmAdLlNN2MnZELKOnrq y6NooUlo2J5tFkjko0PHHyuCNHutmpNaR3dfGOVn3oZcpxsGi75wdVxrlRTn6RMp0p1q 2WiCxiNKF6nRXl6ZWvzCwNCMPwjIRyRhhfNxj3n5acncLeCmyMi+ui3tWOPNYZ29F3ED bNvg== 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=r4gVEI/WwJsRjZDTqv+oTWXfcuwUi/UjDVhVXwXhWOE=; b=pjRyOONj6ZY5cXF0nB3JZyt3AQBSJsLOgogj/0hfU4iOltOuHUe55TYrb+D/8En9Ze MK544458r4XUpabZK0Tg/S+gGVV7tl4cP5wbrY5deKhuWoN1trI3icK2D/UGrwy2rAQR saBZvyRpHDZVmPE792VuYbMexC7ndrlsFKz6s26S9fdHOzE7lqJgc0TGMsYVMdnL0XEW aJ46jlfgOzqayBVo9IFq0Fh35NJ7j+7AAkOw7qhw2arI4i0rFt7G+16Ee91KOwGqBgXL ZGLFqF5aAkaBenw7FS2L82T1YwIwdrmKx1R55obN81kX3CBYl0MDE9DpFBSJPNpNw5pb Y1kA== X-Gm-Message-State: APjAAAWVHlu7W/W21ttwG5joPiCB7VraUTtD5NCDOhv417JEE+Iiuf05 jMceTEP9egdyW0Fr+y8QaDgdtIu+Etl45eB3QDxNuw== X-Google-Smtp-Source: APXvYqx4pwKMTd/1nGHd66IynJvYlUv5LQhGXWDUPJYdbdeITV5yqhUEn3tuE6tzM4KfFJDI6kheDeL1S4wbgNjYdKE= X-Received: by 2002:a67:ce93:: with SMTP id c19mr29979539vse.64.1575301023626; Mon, 02 Dec 2019 07:37:03 -0800 (PST) MIME-Version: 1.0 References: <20191122112621.204798-1-glider@google.com> <20191122112621.204798-23-glider@google.com> In-Reply-To: <20191122112621.204798-23-glider@google.com> From: Marco Elver Date: Mon, 2 Dec 2019 16:36:51 +0100 Message-ID: Subject: Re: [PATCH RFC v3 22/36] kmsan: mm: call KMSAN hooks from SLUB code To: Alexander Potapenko Cc: Andrew Morton , Vegard Nossum , Dmitry Vyukov , Linux Memory Management List , Al Viro , Andreas Dilger , 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" 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 Fri, 22 Nov 2019 at 12:27, wrote: > > In order to report uninitialized memory coming from heap allocations > KMSAN has to poison them unless they're created with __GFP_ZERO. > > It's handy that we need KMSAN hooks in the places where > init_on_alloc/init_on_free initialization is performed. > > Signed-off-by: Alexander Potapenko > To: Alexander Potapenko > Cc: Andrew Morton > Cc: Vegard Nossum > Cc: Dmitry Vyukov > Cc: linux-mm@kvack.org > --- > v3: > - reverted unrelated whitespace changes > > Change-Id: I51103b7981d3aabed747d0c85cbdc85568665871 > --- > mm/slub.c | 34 +++++++++++++++++++++++++++++----- > 1 file changed, 29 insertions(+), 5 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index b25c807a111f..b5d2be1ac755 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -21,6 +21,8 @@ > #include > #include > #include > +#include > +#include /* KMSAN_INIT_VALUE */ > #include > #include > #include > @@ -285,17 +287,27 @@ static void prefetch_freepointer(const struct kmem_cache *s, void *object) > prefetch(object + s->offset); > } > > +/* > + * When running under KMSAN, get_freepointer_safe() may return an uninitialized > + * pointer value in the case the current thread loses the race for the next > + * memory chunk in the freelist. In that case this_cpu_cmpxchg_double() in > + * slab_alloc_node() will fail, so the uninitialized value won't be used, but > + * KMSAN will still check all arguments of cmpxchg because of imperfect > + * handling of inline assembly. > + * To work around this problem, use KMSAN_INIT_VALUE() to force initialize the > + * return value of get_freepointer_safe(). > + */ Isn't this a general problem with cmpxchg? I.e. does other code using it have the same problem? Would it be better to just use KMSAN_INIT_VALUE in cmpxchg, rather than having the one-off workaround here? Thanks, -- Marco