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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 222F2C2D0E4 for ; Wed, 25 Nov 2020 00:47:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C346E21741 for ; Wed, 25 Nov 2020 00:47:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="A6/g4yiH" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727882AbgKYAqk (ORCPT ); Tue, 24 Nov 2020 19:46:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727495AbgKYAqj (ORCPT ); Tue, 24 Nov 2020 19:46:39 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61347C0613D4; Tue, 24 Nov 2020 16:46:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=nqi5GITho3z+SfilHsBCZVHw/SyTqLLJCGfQpf9o3uc=; b=A6/g4yiHt9hfRYsnfjLurXxAAd JCP/BYsja1/nM5Tmri1eIdjD1AIAC80NOPB2lM2HDjRkvWnsJ5b7q65xPK+h9s5YsnUr8qtMafdwI gjNcOZ2WuW1uR/9Uy2JnTxhKUJPzC2EwihfRH6FoD14vG8Mm2dYl4nnTEPtcgsv7ISEjakwm2Ip9Q cF9cbvrQlrLQw1aKr4Fx99mcB/Ui/zM1jAOmRkTEh6rol5+GNHn8J/jQ3qRF1sR3wAb/lBOXvj9f/ ahYWw7eXJthvk5mSgZ1q4qJ1dD/5+uphFikmUnVErtdZLT/7m4ZBK/ArtiNSpgNCfyPF4OjDa6Ppr 0VzBHdQQ==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1khix6-00075q-Sg; Wed, 25 Nov 2020 00:46:33 +0000 Date: Wed, 25 Nov 2020 00:46:32 +0000 From: Matthew Wilcox To: Sebastian Andrzej Siewior Cc: Naresh Kamboju , open list , Linux-Next Mailing List , linux-mm , lkft-triage@lists.linaro.org, LTP List , Andrew Morton , torvalds@linuxfoundation.org, Yang Shi , Jan Kara , Michal Hocko , Thomas Gleixner , Mel Gorman , Song Liu , Zi Yan , vtolkm@googlemail.com, Marek Szyprowski , Arnd Bergmann Subject: Re: kernel BUG at mm/highmem.c:417! invalid opcode: 0000 EIP: zero_user_segments Message-ID: <20201125004632.GG4327@casper.infradead.org> References: <20201124171628.dk6tle5lh3sx2jxg@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201124171628.dk6tle5lh3sx2jxg@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 24, 2020 at 06:16:28PM +0100, Sebastian Andrzej Siewior wrote: > On 2020-11-24 18:52:44 [+0530], Naresh Kamboju wrote: > > While running LTP test case access01 the following kernel BUG > > noticed on linux next 20201124 tag kernel on i386. > > > > git short log: > > ---------------- > > git log --oneline next-20201120..next-20201124 -- mm/highmem.c > > d9927d46febf Merge branch 'akpm-current/current' > > 72d22a0d0e86 mm: support THPs in zero_user_segments > > 2a656cad337e mm/highmem: Take kmap_high_get() properly into account > > > > Please find these easy steps to reproduce the kernel build and boot. > > This BUG_ON() is in zero_user_segments() which ash been added in commit > 72d22a0d0e86 mm: support THPs in zero_user_segments > > > [ 50.852189] kernel BUG at mm/highmem.c:417! > > I managed to capture one invocation with: > zero_user_segments(0xd4367a90, > 0x1000, 0x1000, > 0x0, 0x50) > page_compound() -> 1 > page_size() -> 4096 Thanks for debugging this! I didn't realise start1 was allowed to be less than start2. Try this ... (systemd is sabotaging my efforts to test an i386 kernel) diff --git a/mm/highmem.c b/mm/highmem.c index 3e1087f2b735..6306a535dd9c 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -369,46 +369,39 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1, BUG_ON(end1 > page_size(page) || end2 > page_size(page)); for (i = 0; i < compound_nr(page); i++) { - void *kaddr; - unsigned this_end; + void *kaddr = NULL; - if (end1 == 0 && start2 >= PAGE_SIZE) { - start2 -= PAGE_SIZE; - end2 -= PAGE_SIZE; - continue; - } + if (start1 < PAGE_SIZE || start2 < PAGE_SIZE) + kaddr = kmap_atomic(page + i); if (start1 >= PAGE_SIZE) { start1 -= PAGE_SIZE; end1 -= PAGE_SIZE; - if (start2) { - start2 -= PAGE_SIZE; - end2 -= PAGE_SIZE; - } - continue; - } - - kaddr = kmap_atomic(page + i); + } else { + unsigned this_end = min_t(unsigned, end1, PAGE_SIZE); - this_end = min_t(unsigned, end1, PAGE_SIZE); - if (end1 > start1) - memset(kaddr + start1, 0, this_end - start1); - end1 -= this_end; - start1 = 0; + if (end1 > start1) + memset(kaddr + start1, 0, this_end - start1); + end1 -= this_end; + start1 = 0; + } if (start2 >= PAGE_SIZE) { start2 -= PAGE_SIZE; end2 -= PAGE_SIZE; } else { - this_end = min_t(unsigned, end2, PAGE_SIZE); + unsigned this_end = min_t(unsigned, end2, PAGE_SIZE); + if (end2 > start2) memset(kaddr + start2, 0, this_end - start2); end2 -= this_end; start2 = 0; } - kunmap_atomic(kaddr); - flush_dcache_page(page + i); + if (kaddr) { + kunmap_atomic(kaddr); + flush_dcache_page(page + i); + } if (!end1 && !end2) break;