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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 3A5EEC54FCF for ; Wed, 25 Mar 2020 03:19:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19C5C20724 for ; Wed, 25 Mar 2020 03:19:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727357AbgCYDTf (ORCPT ); Tue, 24 Mar 2020 23:19:35 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:62908 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727279AbgCYDTe (ORCPT ); Tue, 24 Mar 2020 23:19:34 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02P32brF014122; Tue, 24 Mar 2020 23:19:26 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ywf2hrjaa-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 24 Mar 2020 23:19:26 -0400 Received: from m0098414.ppops.net (m0098414.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 02P396qu080221; Tue, 24 Mar 2020 23:19:25 -0400 Received: from ppma03dal.us.ibm.com (b.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.11]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ywf2hrj9y-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 24 Mar 2020 23:19:25 -0400 Received: from pps.filterd (ppma03dal.us.ibm.com [127.0.0.1]) by ppma03dal.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id 02P3BB4w009210; Wed, 25 Mar 2020 03:19:25 GMT Received: from b03cxnp08027.gho.boulder.ibm.com (b03cxnp08027.gho.boulder.ibm.com [9.17.130.19]) by ppma03dal.us.ibm.com with ESMTP id 2ywaw9nkw5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 25 Mar 2020 03:19:25 +0000 Received: from b03ledav002.gho.boulder.ibm.com (b03ledav002.gho.boulder.ibm.com [9.17.130.233]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02P3JNND16384596 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 25 Mar 2020 03:19:23 GMT Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B17E3136051; Wed, 25 Mar 2020 03:19:23 +0000 (GMT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 21DC3136053; Wed, 25 Mar 2020 03:19:21 +0000 (GMT) Received: from skywalker.ibmuc.com (unknown [9.199.32.190]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 25 Mar 2020 03:19:20 +0000 (GMT) From: "Aneesh Kumar K.V" To: linux-mm@kvack.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, "Aneesh Kumar K.V" , Baoquan He , Sachin Sant Subject: [PATCH] mm/sparse: Fix kernel crash with pfn_section_valid check Date: Wed, 25 Mar 2020 08:49:14 +0530 Message-Id: <20200325031914.107660-1-aneesh.kumar@linux.ibm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-24_10:2020-03-23,2020-03-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 impostorscore=0 suspectscore=2 adultscore=0 priorityscore=1501 spamscore=0 phishscore=0 malwarescore=0 mlxlogscore=999 clxscore=1015 mlxscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003250021 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fixes the below crash BUG: Kernel NULL pointer dereference on read at 0x00000000 Faulting instruction address: 0xc000000000c3447c Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries CPU: 11 PID: 7519 Comm: lt-ndctl Not tainted 5.6.0-rc7-autotest #1 ... NIP [c000000000c3447c] vmemmap_populated+0x98/0xc0 LR [c000000000088354] vmemmap_free+0x144/0x320 Call Trace: section_deactivate+0x220/0x240 __remove_pages+0x118/0x170 arch_remove_memory+0x3c/0x150 memunmap_pages+0x1cc/0x2f0 devm_action_release+0x30/0x50 release_nodes+0x2f8/0x3e0 device_release_driver_internal+0x168/0x270 unbind_store+0x130/0x170 drv_attr_store+0x44/0x60 sysfs_kf_write+0x68/0x80 kernfs_fop_write+0x100/0x290 __vfs_write+0x3c/0x70 vfs_write+0xcc/0x240 ksys_write+0x7c/0x140 system_call+0x5c/0x68 With commit: d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case") section_mem_map is set to NULL after depopulate_section_mem(). This was done so that pfn_page() can work correctly with kernel config that disables SPARSEMEM_VMEMMAP. With that config pfn_to_page does __section_mem_map_addr(__sec) + __pfn; where static inline struct page *__section_mem_map_addr(struct mem_section *section) { unsigned long map = section->section_mem_map; map &= SECTION_MAP_MASK; return (struct page *)map; } Now with SPASEMEM_VMEMAP enabled, mem_section->usage->subsection_map is used to check the pfn validity (pfn_valid()). Since section_deactivate release mem_section->usage if a section is fully deactivated, pfn_valid() check after a subsection_deactivate cause a kernel crash. static inline int pfn_valid(unsigned long pfn) { ... return early_section(ms) || pfn_section_valid(ms, pfn); } where static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn) { int idx = subsection_map_index(pfn); return test_bit(idx, ms->usage->subsection_map); } Avoid this by clearing SECTION_HAS_MEM_MAP when mem_section->usage is freed. Fixes: d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case") Cc: Baoquan He Reported-by: Sachin Sant Signed-off-by: Aneesh Kumar K.V --- mm/sparse.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/sparse.c b/mm/sparse.c index aadb7298dcef..3012d1f3771a 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -781,6 +781,8 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages, ms->usage = NULL; } memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); + /* Mark the section invalid */ + ms->section_mem_map &= ~SECTION_HAS_MEM_MAP; } if (section_is_early && memmap) -- 2.25.1