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Mon, 06 Jul 2020 03:57:57 -0400 X-MC-Unique: kasC5dELNYGpGcX6SOJh6A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6317F800C64; Mon, 6 Jul 2020 07:57:55 +0000 (UTC) Received: from [10.36.114.3] (ovpn-114-3.ams2.redhat.com [10.36.114.3]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7EDB571669; Mon, 6 Jul 2020 07:57:51 +0000 (UTC) Subject: Re: [PATCH 2/3] mm/memory_hotplug: harden try_offline_node against bogus nid To: Jia He , Catalin Marinas , Will Deacon Cc: Andrew Morton , Mike Rapoport , Baoquan He , Chuhong Yuan , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Kaly Xin References: <20200706011947.184166-1-justin.he@arm.com> <20200706011947.184166-3-justin.he@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200706011947.184166-3-justin.he@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Rspamd-Queue-Id: 0B08E18229818 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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: On 06.07.20 03:19, Jia He wrote: > When testing the remove_memory path of dax pmem, there will be a panic = with > call trace: > try_remove_memory+0x84/0x170 > remove_memory+0x38/0x58 > dev_dax_kmem_remove+0x3c/0x84 [kmem] > device_release_driver_internal+0xfc/0x1c8 > device_release_driver+0x28/0x38 > bus_remove_device+0xd4/0x158 > device_del+0x160/0x3a0 > unregister_dev_dax+0x30/0x68 > devm_action_release+0x20/0x30 > release_nodes+0x150/0x240 > devres_release_all+0x6c/0x1d0 > device_release_driver_internal+0x10c/0x1c8 > driver_detach+0xac/0x170 > bus_remove_driver+0x64/0x130 > driver_unregister+0x34/0x60 > dax_pmem_exit+0x14/0xffc4 [dax_pmem] > __arm64_sys_delete_module+0x18c/0x2d0 > el0_svc_common.constprop.2+0x78/0x168 > do_el0_svc+0x34/0xa0 > el0_sync_handler+0xe0/0x188 > el0_sync+0x164/0x180 >=20 > It is caused by the bogus nid (-1). Although the root cause is pmem dax > translates from pxm to node_id incorrectly due to numa_off, it is worth > hardening the codes in try_offline_node(), quiting if !pgdat. >=20 > Signed-off-by: Jia He > --- > mm/memory_hotplug.c | 3 +++ > 1 file changed, 3 insertions(+) >=20 > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index da374cd3d45b..e1e290577b45 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1680,6 +1680,9 @@ void try_offline_node(int nid) > pg_data_t *pgdat =3D NODE_DATA(nid); > int rc; > =20 > + if (WARN_ON(!pgdat)) > + return; > + > /* > * If the node still spans pages (especially ZONE_DEVICE), don't > * offline it. A node spans memory after move_pfn_range_to_zone(), >=20 Hm. If I am not wrong, somebody used add_memory() with another nid than try_remove_memory()? Or did we pass the node_possible(nid) check in add_memory_resource(), and succeeded to add to nid=3D=3D-1? Having that said, this feels somewhat wrong, especially checking against pgdat down in try_offline_node(). It really has to be the same nid as used when adding - and that nid has to be sane. --=20 Thanks, David / dhildenb