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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C236C433EF for ; Tue, 9 Nov 2021 17:15:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F10AA61207 for ; Tue, 9 Nov 2021 17:15:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org F10AA61207 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 482AB6B009B; Tue, 9 Nov 2021 12:15:42 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 431CD6B009C; Tue, 9 Nov 2021 12:15:42 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 347D66B009D; Tue, 9 Nov 2021 12:15:42 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0249.hostedemail.com [216.40.44.249]) by kanga.kvack.org (Postfix) with ESMTP id 191876B009B for ; Tue, 9 Nov 2021 12:15:42 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id EEDAD7C5CE for ; Tue, 9 Nov 2021 17:15:37 +0000 (UTC) X-FDA: 78790043556.17.0C4487E Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf29.hostedemail.com (Postfix) with ESMTP id 4F5E89000675 for ; Tue, 9 Nov 2021 17:15:35 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id F3E571FD34; Tue, 9 Nov 2021 17:15:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1636478134; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=w2u1c/OVbCzJIJ5761FcTJUE1XzuOMfSX3Bnp8Mme7s=; b=ZwQV9ABZLTcCLrPTJXvGjA+CksqOScnFQ8y0snD8Rj9xiiHPpSSUpj06oAM7Oxqgy0kvMt Jxkr/KioI9GmfnXam3MDeBKl9K/OCjxRfLkcFPCuRSbcGuZEhgA6MLKgWN+4ynU3ZVoEI7 LIW5/W375caR/JxKMeZFxQZVyx26PGo= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id AFE77A3B83; Tue, 9 Nov 2021 17:15:33 +0000 (UTC) Date: Tue, 9 Nov 2021 18:15:33 +0100 From: Michal Hocko To: Eric Dumazet Cc: Alexey Makhalov , linux-mm@kvack.org, Andrew Morton , David Hildenbrand , Oscar Salvador , Dennis Zhou , Tejun Heo , Christoph Lameter , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages Message-ID: References: <908909e0-4815-b580-7ff5-d824d36a141c@redhat.com> <20211108202325.20304-1-amakhalov@vmware.com> <2e191db3-286f-90c6-bf96-3f89891e9926@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2e191db3-286f-90c6-bf96-3f89891e9926@gmail.com> Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=ZwQV9ABZ; spf=pass (imf29.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 4F5E89000675 X-Stat-Signature: 98jptyz11zsha5m85hdmnqw715dktfi9 X-HE-Tag: 1636478135-970287 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 Mon 08-11-21 18:08:52, Eric Dumazet wrote: > > > On 11/8/21 12:23 PM, Alexey Makhalov wrote: > > There is a kernel panic caused by pcpu_alloc_pages() passing > > offlined and uninitialized node to alloc_pages_node() leading > > to panic by NULL dereferencing uninitialized NODE_DATA(nid). > > > > CPU2 has been hot-added > > BUG: unable to handle page fault for address: 0000000000001608 > > #PF: supervisor read access in kernel mode > > #PF: error_code(0x0000) - not-present page > > PGD 0 P4D 0 > > Oops: 0000 [#1] SMP PTI > > CPU: 0 PID: 1 Comm: systemd Tainted: G E 5.15.0-rc7+ #11 > > Hardware name: VMware, Inc. VMware7,1/440BX Desktop Reference Platform, BIOS VMW > > > > RIP: 0010:__alloc_pages+0x127/0x290 > > Code: 4c 89 f0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 44 89 e0 48 8b 55 b8 c1 e8 0c 83 e0 01 88 45 d0 4c 89 c8 48 85 d2 0f 85 1a 01 00 00 <45> 3b 41 08 0f 82 10 01 00 00 48 89 45 c0 48 8b 00 44 89 e2 81 e2 > > RSP: 0018:ffffc900006f3bc8 EFLAGS: 00010246 > > RAX: 0000000000001600 RBX: 0000000000000000 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000cc2 > > RBP: ffffc900006f3c18 R08: 0000000000000001 R09: 0000000000001600 > > R10: ffffc900006f3a40 R11: ffff88813c9fffe8 R12: 0000000000000cc2 > > R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000cc2 > > FS: 00007f27ead70500(0000) GS:ffff88807ce00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000000001608 CR3: 000000000582c003 CR4: 00000000001706b0 > > Call Trace: > > pcpu_alloc_pages.constprop.0+0xe4/0x1c0 > > pcpu_populate_chunk+0x33/0xb0 > > pcpu_alloc+0x4d3/0x6f0 > > __alloc_percpu_gfp+0xd/0x10 > > alloc_mem_cgroup_per_node_info+0x54/0xb0 > > mem_cgroup_alloc+0xed/0x2f0 > > mem_cgroup_css_alloc+0x33/0x2f0 > > css_create+0x3a/0x1f0 > > cgroup_apply_control_enable+0x12b/0x150 > > cgroup_mkdir+0xdd/0x110 > > kernfs_iop_mkdir+0x4f/0x80 > > vfs_mkdir+0x178/0x230 > > do_mkdirat+0xfd/0x120 > > __x64_sys_mkdir+0x47/0x70 > > ? syscall_exit_to_user_mode+0x21/0x50 > > do_syscall_64+0x43/0x90 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > Panic can be easily reproduced by disabling udev rule for > > automatic onlining hot added CPU followed by CPU with > > memoryless node (NUMA node with CPU only) hot add. > > > > Hot adding CPU and memoryless node does not bring the node > > to online state. Memoryless node will be onlined only during > > the onlining its CPU. > > > > Node can be in one of the following states: > > 1. not present.(nid == NUMA_NO_NODE) > > 2. present, but offline (nid > NUMA_NO_NODE, node_online(nid) == 0, > > NODE_DATA(nid) == NULL) > > 3. present and online (nid > NUMA_NO_NODE, node_online(nid) > 0, > > NODE_DATA(nid) != NULL) > > > > Percpu code is doing allocations for all possible CPUs. The > > issue happens when it serves hot added but not yet onlined > > CPU when its node is in 2nd state. This node is not ready > > to use, fallback to numa_mem_id(). > > > > Signed-off-by: Alexey Makhalov > > Reviewed-by: David Hildenbrand > > Cc: Andrew Morton > > Cc: David Hildenbrand > > Cc: Michal Hocko > > Cc: Oscar Salvador > > Cc: Dennis Zhou > > Cc: Tejun Heo > > Cc: Christoph Lameter > > Cc: linux-mm@kvack.org > > Cc: linux-kernel@vger.kernel.org > > Cc: stable@vger.kernel.org > > --- > > mm/percpu-vm.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c > > index 2054c9213..f58d73c92 100644 > > --- a/mm/percpu-vm.c > > +++ b/mm/percpu-vm.c > > @@ -84,15 +84,19 @@ static int pcpu_alloc_pages(struct pcpu_chunk *chunk, > > gfp_t gfp) > > { > > unsigned int cpu, tcpu; > > - int i; > > + int i, nid; > > > > gfp |= __GFP_HIGHMEM; > > > > for_each_possible_cpu(cpu) { > > + nid = cpu_to_node(cpu); > > + if (nid == NUMA_NO_NODE || !node_online(nid)) > > + nid = numa_mem_id(); > > Maybe we should fail this fallback if (gfp & __GFP_THISNODE) ? > > Or maybe there is no support for this constraint in per-cpu allocator anyway. I would be really curious about the usecase. Not to mention that pcp allocation would be effectively unusable on any setups with memory less nodes. > I am a bit worried that we do not really know if pages are > allocated on the right node or not. There hasn't been any guarantee like that. Page allocator would fallback to other nodes (in the node distance order) unless __GFP_THISNODE is specified. This patch just papers over the fact that currently we can end up having an invalid numa node associated with a cpu. This is a bug in the initialization code. Even if that is fixed the node fallback is still a real thing that might happen. -- Michal Hocko SUSE Labs