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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 3F091C43381 for ; Sat, 16 Feb 2019 10:55:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05CEA222A1 for ; Sat, 16 Feb 2019 10:55:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gTSYYkp1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728247AbfBPKzR (ORCPT ); Sat, 16 Feb 2019 05:55:17 -0500 Received: from mail-pl1-f194.google.com ([209.85.214.194]:36659 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726219AbfBPKzR (ORCPT ); Sat, 16 Feb 2019 05:55:17 -0500 Received: by mail-pl1-f194.google.com with SMTP id g9so6273364plo.3 for ; Sat, 16 Feb 2019 02:55:16 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=1Ubpr1Ey/DmY/KE61Qrh0yzi4L35UYNNw5PJu00uODc=; b=gTSYYkp1t3MnTZM0YoT8ot7TKpB/68aT35/5SpKN4og5QIhe8orF0G0hFRBEdlhzSZ QUI97HjYOShyGwqv/RBr4sBgk9vJyWEO/KhEYRDTdKe6kqbIepfy1i+jNqeQgQT5i9nx GUT3mzRHk+JnWlSPY2PQ4JzIm2C4WlnViSb8R+UVlPdqwnIYhtEjM3wD/9jy4iHCKAmO d82k+tDkXgOQBBQWmicHzH0OcQPf3Q7Xzm0PhQK0a7GDmXsghgaioI8raZ1m0wk67uD8 2i1TAfvSNY8TgWPw0OuZRv8Wh3Gf7KjwfDCTRQYBPrTOEheaKTZfu7uTA3x1GSXnyf7M GtXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=1Ubpr1Ey/DmY/KE61Qrh0yzi4L35UYNNw5PJu00uODc=; b=eLcoGov7+O1xKpzaMrkAbpsiDP6IQJUIHiyEOesjD6FXLV2xmNcGGhG8P64pw39oeQ P4E51Tz2k7IszuSCSZdV0Tnx7IQnGVNynjpOJuFViooE3Ryv5iqC8vsV4yhfU7rBJYrS z6wP0TjpbydZcKIt+eWOZJmkQ3U8Mqk9vY3WoqoS+TveG+TJr/R/yO+z7Ux0HQKN3cYQ GrLMzASGmONzIfkcVsmDYgi4a69zjo1RtQZtdSEMJzZfCw3F7FGqrchVN7F3bqW7s2x3 tAVbfT0yhyNTMVxQTIduWvDr3aXVBJpjQw6BiJxOVkZZTg9nafpW3reLefaPHcRTUF9l K6vQ== X-Gm-Message-State: AHQUAubRZ9LxTrkLaCGQYo56BbfFqcBpDAK9uadRsobgQoAMmlUUOUgX LE3Tpx9OA6DasvMMFkElgu8= X-Google-Smtp-Source: AHgI3IaJGJ4E5JLUuz+5RAh+KUilztY5KioLABGSyqMSqji8EHYOrI10oopn/wpXsFIzfD3Hl7vpJg== X-Received: by 2002:a17:902:2dc3:: with SMTP id p61mr14670803plb.166.1550314515841; Sat, 16 Feb 2019 02:55:15 -0800 (PST) Received: from localhost (123-243-232-193.tpgi.com.au. [123.243.232.193]) by smtp.gmail.com with ESMTPSA id p12sm17159170pfj.81.2019.02.16.02.55.14 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 16 Feb 2019 02:55:15 -0800 (PST) Date: Sat, 16 Feb 2019 21:55:11 +1100 From: Balbir Singh To: Michael Ellerman Cc: linuxppc-dev@ozlabs.org, aneesh.kumar@linux.vnet.ibm.com, jack@suse.cz, erhard_f@mailbox.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] powerpc/64s: Fix possible corruption on big endian due to pgd/pud_present() Message-ID: <20190216105511.GA31125@350D> References: <20190214062339.7139-1-mpe@ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190214062339.7139-1-mpe@ellerman.id.au> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 14, 2019 at 05:23:39PM +1100, Michael Ellerman wrote: > In v4.20 we changed our pgd/pud_present() to check for _PAGE_PRESENT > rather than just checking that the value is non-zero, e.g.: > > static inline int pgd_present(pgd_t pgd) > { > - return !pgd_none(pgd); > + return (pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT)); > } > > Unfortunately this is broken on big endian, as the result of the > bitwise && is truncated to int, which is always zero because Not sure why that should happen, why is the result an int? What causes the casting of pgd_t & be64 to be truncated to an int. > _PAGE_PRESENT is 0x8000000000000000ul. This means pgd_present() and > pud_present() are always false at compile time, and the compiler > elides the subsequent code. > > Remarkably with that bug present we are still able to boot and run > with few noticeable effects. However under some work loads we are able > to trigger a warning in the ext4 code: > > WARNING: CPU: 11 PID: 29593 at fs/ext4/inode.c:3927 .ext4_set_page_dirty+0x70/0xb0 > CPU: 11 PID: 29593 Comm: debugedit Not tainted 4.20.0-rc1 #1 > ... > NIP .ext4_set_page_dirty+0x70/0xb0 > LR .set_page_dirty+0xa0/0x150 > Call Trace: > .set_page_dirty+0xa0/0x150 > .unmap_page_range+0xbf0/0xe10 > .unmap_vmas+0x84/0x130 > .unmap_region+0xe8/0x190 > .__do_munmap+0x2f0/0x510 > .__vm_munmap+0x80/0x110 > .__se_sys_munmap+0x14/0x30 > system_call+0x5c/0x70 > > The fix is simple, we need to convert the result of the bitwise && to > an int before returning it. > > Thanks to Jan Kara and Aneesh for help with debugging. > > Fixes: da7ad366b497 ("powerpc/mm/book3s: Update pmd_present to look at _PAGE_PRESENT bit") > Cc: stable@vger.kernel.org # v4.20+ > Reported-by: Erhard F. > Reviewed-by: Aneesh Kumar K.V > Signed-off-by: Michael Ellerman > --- > arch/powerpc/include/asm/book3s/64/pgtable.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h > index c9bfe526ca9d..d8c8d7c9df15 100644 > --- a/arch/powerpc/include/asm/book3s/64/pgtable.h > +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h > @@ -904,7 +904,7 @@ static inline int pud_none(pud_t pud) > > static inline int pud_present(pud_t pud) > { > - return (pud_raw(pud) & cpu_to_be64(_PAGE_PRESENT)); > + return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PRESENT)); > } > > extern struct page *pud_page(pud_t pud); > @@ -951,7 +951,7 @@ static inline int pgd_none(pgd_t pgd) > > static inline int pgd_present(pgd_t pgd) > { > - return (pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT)); > + return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT)); > } > Care to put a big FAT warning, so that we don't repeat this again (as in authors planning on changing these bits). Balbir Singh.