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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 EF3B1C2D0BE for ; Mon, 9 Dec 2019 17:48:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A50E920836 for ; Mon, 9 Dec 2019 17:48:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fR9binU0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A50E920836 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 548546B27E8; Mon, 9 Dec 2019 12:48:52 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4F8ED6B27E9; Mon, 9 Dec 2019 12:48:52 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3E86C6B27EA; Mon, 9 Dec 2019 12:48:52 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0204.hostedemail.com [216.40.44.204]) by kanga.kvack.org (Postfix) with ESMTP id 292B76B27E8 for ; Mon, 9 Dec 2019 12:48:52 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id C869A282C for ; Mon, 9 Dec 2019 17:48:51 +0000 (UTC) X-FDA: 76246338462.13.look84_6a60d1e066113 X-HE-Tag: look84_6a60d1e066113 X-Filterd-Recvd-Size: 7427 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-1.mimecast.com [205.139.110.61]) by imf23.hostedemail.com (Postfix) with ESMTP for ; Mon, 9 Dec 2019 17:48:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575913730; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5j9y6uTzLH6AC77P2ufw4QrIfhyaBDvoWP5b6gJS+oc=; b=fR9binU0UU8PsjwemD+N7GlcTUGRDom3vaCWYaWIpRNwVhvuN9kXKJlWPMnFrnFKxkxkov 4ZwIfT00HNtP7g7gfQcS6AaXZeKZmIMwhqWLZsGH7iejU1RP9OpTGGkMtj5XstVrycMvJ4 2v7tBZV9Fz7mCwkLZWmHhXlb0EjvhBs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-362-Fe-49BicNvahBHQY8FMnhg-1; Mon, 09 Dec 2019 12:48:47 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 872581005514; Mon, 9 Dec 2019 17:48:45 +0000 (UTC) Received: from t460s.redhat.com (ovpn-116-214.ams2.redhat.com [10.36.116.214]) by smtp.corp.redhat.com (Postfix) with ESMTP id 143951001B03; Mon, 9 Dec 2019 17:48:42 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , stable@vger.kernel.org, Naoya Horiguchi , Pavel Tatashin , Andrew Morton , Steven Sistare , Michal Hocko , Daniel Jordan , Bob Picco , Oscar Salvador Subject: [PATCH v1 1/3] mm: fix uninitialized memmaps on a partially populated last section Date: Mon, 9 Dec 2019 18:48:34 +0100 Message-Id: <20191209174836.11063-2-david@redhat.com> In-Reply-To: <20191209174836.11063-1-david@redhat.com> References: <20191209174836.11063-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: Fe-49BicNvahBHQY8FMnhg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII 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: If max_pfn is not aligned to a section boundary, we can easily run into BUGs. This can e.g., be triggered on x86-64 under QEMU by specifying a memory size that is not a multiple of 128MB (e.g., 4097MB, but also 4160MB). I was told that on real HW, we can easily have this scenario (esp., one of the main reasons sub-section hotadd of devmem was added). The issue is, that we have a valid memmap (pfn_valid()) for the whole section, and the whole section will be marked "online". pfn_to_online_page() will succeed, but the memmap contains garbage. E.g., doing a "cat /proc/kpageflags > /dev/null" results in [ 303.218313] BUG: unable to handle page fault for address: ffffffffffffff= fe [ 303.218899] #PF: supervisor read access in kernel mode [ 303.219344] #PF: error_code(0x0000) - not-present page [ 303.219787] PGD 12614067 P4D 12614067 PUD 12616067 PMD 0 [ 303.220266] Oops: 0000 [#1] SMP NOPTI [ 303.220587] CPU: 0 PID: 424 Comm: cat Not tainted 5.4.0-next-20191128+ #= 17 [ 303.221169] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS = rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4 [ 303.222140] RIP: 0010:stable_page_flags+0x4d/0x410 [ 303.222554] Code: f3 ff 41 89 c0 48 b8 00 00 00 00 01 00 00 00 45 84 c0 = 0f 85 cd 02 00 00 48 8b 53 08 48 8b 2b 48f [ 303.224135] RSP: 0018:ffff9f5980187e58 EFLAGS: 00010202 [ 303.224576] RAX: fffffffffffffffe RBX: ffffda1285004000 RCX: ffff9f59801= 87dd4 [ 303.225178] RDX: 0000000000000001 RSI: ffffffff92662420 RDI: 00000000000= 00246 [ 303.225789] RBP: ffffffffffffffff R08: 0000000000000000 R09: 00000000000= 00000 [ 303.226405] R10: 0000000000000000 R11: 0000000000000000 R12: 00007f31d07= 0e000 [ 303.227012] R13: 0000000000140100 R14: 00007f31d070e800 R15: ffffda12850= 04000 [ 303.227629] FS: 00007f31d08f6580(0000) GS:ffff90a6bba00000(0000) knlGS:= 0000000000000000 [ 303.228329] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 303.228820] CR2: fffffffffffffffe CR3: 00000001332a2000 CR4: 00000000000= 006f0 [ 303.229438] Call Trace: [ 303.229654] kpageflags_read.cold+0x57/0xf0 [ 303.230016] proc_reg_read+0x3c/0x60 [ 303.230332] vfs_read+0xc2/0x170 [ 303.230614] ksys_read+0x65/0xe0 [ 303.230898] do_syscall_64+0x5c/0xa0 [ 303.231216] entry_SYSCALL_64_after_hwframe+0x49/0xbe This patch fixes that by at least zero-ing out that memmap (so e.g., page_to_pfn() will not crash). Commit 907ec5fca3dc ("mm: zero remaining unavailable struct pages") tried to fix a similar issue, but forgot to consider this special case. After this patch, there are still problems to solve. E.g., not all of these pages falling into a memory hole will actually get initialized later and set PageReserved - they are only zeroed out - but at least the immediate crashes are gone. A follow-up patch will take care of this. Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap"= ) Cc: # v4.15+ Cc: Naoya Horiguchi Cc: Pavel Tatashin Cc: Andrew Morton Cc: Steven Sistare Cc: Michal Hocko Cc: Daniel Jordan Cc: Bob Picco Cc: Oscar Salvador Signed-off-by: David Hildenbrand --- mm/page_alloc.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 62dcd6b76c80..1eb2ce7c79e4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6932,7 +6932,8 @@ static u64 zero_pfn_range(unsigned long spfn, unsigne= d long epfn) * This function also addresses a similar issue where struct pages are lef= t * uninitialized because the physical address range is not covered by * memblock.memory or memblock.reserved. That could happen when memblock - * layout is manually configured via memmap=3D. + * layout is manually configured via memmap=3D, or when the highest physic= al + * address (max_pfn) does not end on a section boundary. */ void __init zero_resv_unavail(void) { @@ -6950,7 +6951,16 @@ void __init zero_resv_unavail(void) =09=09=09pgcnt +=3D zero_pfn_range(PFN_DOWN(next), PFN_UP(start)); =09=09next =3D end; =09} -=09pgcnt +=3D zero_pfn_range(PFN_DOWN(next), max_pfn); + +=09/* +=09 * Early sections always have a fully populated memmap for the whole +=09 * section - see pfn_valid(). If the last section has holes at the +=09 * end and that section is marked "online", the memmap will be +=09 * considered initialized. Make sure that memmap has a well defined +=09 * state. +=09 */ +=09pgcnt +=3D zero_pfn_range(PFN_DOWN(next), +=09=09=09=09round_up(max_pfn, PAGES_PER_SECTION)); =20 =09/* =09 * Struct pages that do not have backing memory. This could be because --=20 2.21.0