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,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 79CF6C2D0EE for ; Tue, 31 Mar 2020 09:08:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E5B32137B for ; Tue, 31 Mar 2020 09:08:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585645717; bh=0YWN7uw21TRiOC+QdCdepE6qoKwvoYs7NgnThVS7TJk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=VuqAMHv8mVBWxhg4a3MQWeHAD34fwMO/DK4tX5O4kcebvb9ug17UtBfAmuUukC4un gQXQxHHApcTMhWxlmkC5uS6h3HTxQh1M8XJl49esQEUrKsB2MawIGR3D4y79ic2DPP 45Tlg2tzGOLbAEclNGCViIAfwAz9w7XjRVTYa7pA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731000AbgCaJIc (ORCPT ); Tue, 31 Mar 2020 05:08:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:51022 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730570AbgCaJIc (ORCPT ); Tue, 31 Mar 2020 05:08:32 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2AB4620787; Tue, 31 Mar 2020 09:08:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585645711; bh=0YWN7uw21TRiOC+QdCdepE6qoKwvoYs7NgnThVS7TJk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ikkR2CbCmz25jxnslqQraa/S+8H+9Co9d68kJCFlII/SabMcbt/NNaqwksfcA8CR+ FtxSg2gDshXMtHdE9/J6MDVTfKVsCpkGLDvK24mqjB+R3X/xN8DPIYMv3FZWOt14y9 5EPXNaVkaFwhIcVFRCvzl04cOmx2HRx5I6xHBXdg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sachin Sant , "Aneesh Kumar K.V" , Andrew Morton , Baoquan He , Wei Yang , Michal Hocko , Pankaj Gupta , Michael Ellerman , Dan Williams , David Hildenbrand , Oscar Salvador , Mike Rapoport , Linus Torvalds Subject: [PATCH 5.5 113/170] mm/sparse: fix kernel crash with pfn_section_valid check Date: Tue, 31 Mar 2020 10:58:47 +0200 Message-Id: <20200331085436.185695146@linuxfoundation.org> X-Mailer: git-send-email 2.26.0 In-Reply-To: <20200331085423.990189598@linuxfoundation.org> References: <20200331085423.990189598@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Aneesh Kumar K.V commit b943f045a9af9fd02f923e43fe8d7517e9961701 upstream. Fix the crash like this: 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 The crash is due to NULL dereference at test_bit(idx, ms->usage->subsection_map); due to ms->usage = NULL in pfn_section_valid() 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. For architectures like ppc64 where large pages are used for vmmemap mapping (16MB), a specific vmemmap mapping can cover multiple sections. Hence before a vmemmap mapping page can be freed, the kernel needs to make sure there are no valid sections within that mapping. Clearing the section valid bit before depopulate_section_memap enables this. [aneesh.kumar@linux.ibm.com: add comment] Link: http://lkml.kernel.org/r/20200326133235.343616-1-aneesh.kumar@linux.ibm.comLink: http://lkml.kernel.org/r/20200325031914.107660-1-aneesh.kumar@linux.ibm.com Fixes: d41e2f3bd546 ("mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case") Reported-by: Sachin Sant Signed-off-by: Aneesh Kumar K.V Signed-off-by: Andrew Morton Tested-by: Sachin Sant Reviewed-by: Baoquan He Reviewed-by: Wei Yang Acked-by: Michal Hocko Acked-by: Pankaj Gupta Cc: Michael Ellerman Cc: Dan Williams Cc: David Hildenbrand Cc: Oscar Salvador Cc: Mike Rapoport Cc: Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/sparse.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/mm/sparse.c +++ b/mm/sparse.c @@ -791,6 +791,12 @@ static void section_deactivate(unsigned ms->usage = NULL; } memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); + /* + * Mark the section invalid so that valid_section() + * return false. This prevents code from dereferencing + * ms->usage array. + */ + ms->section_mem_map &= ~SECTION_HAS_MEM_MAP; } if (section_is_early && memmap)