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=-6.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 F39FBC433E7 for ; Fri, 9 Oct 2020 13:22:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 84FAC2065C for ; Fri, 9 Oct 2020 13:22:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 84FAC2065C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B69586B005D; Fri, 9 Oct 2020 09:22:38 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AF1F7900002; Fri, 9 Oct 2020 09:22:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9B9AE6B0068; Fri, 9 Oct 2020 09:22:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0153.hostedemail.com [216.40.44.153]) by kanga.kvack.org (Postfix) with ESMTP id 6CE156B005D for ; Fri, 9 Oct 2020 09:22:38 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 0185C180AD806 for ; Fri, 9 Oct 2020 13:22:38 +0000 (UTC) X-FDA: 77352451596.06.comb26_4812caa271e0 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id D43BD101B9AF2 for ; Fri, 9 Oct 2020 13:22:37 +0000 (UTC) X-HE-Tag: comb26_4812caa271e0 X-Filterd-Recvd-Size: 6833 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by imf13.hostedemail.com (Postfix) with ESMTP for ; Fri, 9 Oct 2020 13:22:36 +0000 (UTC) IronPort-SDR: jZuNTK1WkVn6XuOYGuBMIbHGjRmAqLMOa5ekRvt4n+4OnzDDaati93eSNymUMcZwq4FMLcyC6F xxw8CLx13/cQ== X-IronPort-AV: E=McAfee;i="6000,8403,9768"; a="164693515" X-IronPort-AV: E=Sophos;i="5.77,355,1596524400"; d="scan'208";a="164693515" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2020 06:22:33 -0700 IronPort-SDR: +5LjZD96jvljrYhNroneAvXZdYYE0/4c94V4Lj785HahXBEiV+UaeyqSL132kgdjY//7BAvwjm LOoURq7HYfEg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,355,1596524400"; d="scan'208";a="349827159" Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga002.fm.intel.com with ESMTP; 09 Oct 2020 06:22:30 -0700 Received: by black.fi.intel.com (Postfix, from userid 1000) id B942F15C; Fri, 9 Oct 2020 16:22:29 +0300 (EEST) Date: Fri, 9 Oct 2020 16:22:29 +0300 From: "Kirill A. Shutemov" To: "Huang, Ying" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rafael Aquini , Hugh Dickins , Andrea Arcangeli Subject: Re: [PATCH] mm: Fix a race during split THP Message-ID: <20201009132229.yzodvvk6h6yk65op@black.fi.intel.com> References: <20201009073647.1531083-1-ying.huang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201009073647.1531083-1-ying.huang@intel.com> 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 Fri, Oct 09, 2020 at 03:36:47PM +0800, Huang, Ying wrote: > From: Huang Ying > > It is reported that the following bug is triggered if the HDD is used as swap > device, > > [ 5758.157556] BUG: kernel NULL pointer dereference, address: 0000000000000007 > [ 5758.165331] #PF: supervisor write access in kernel mode > [ 5758.171161] #PF: error_code(0x0002) - not-present page > [ 5758.176894] PGD 0 P4D 0 > [ 5758.179721] Oops: 0002 [#1] SMP PTI > [ 5758.183614] CPU: 10 PID: 316 Comm: kswapd1 Kdump: loaded Tainted: G S --------- --- 5.9.0-0.rc3.1.tst.el8.x86_64 #1 > [ 5758.196717] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.02.01.0002.082220131453 08/22/2013 > [ 5758.208176] RIP: 0010:split_swap_cluster+0x47/0x60 > [ 5758.213522] Code: c1 e3 06 48 c1 eb 0f 48 8d 1c d8 48 89 df e8 d0 20 6a 00 80 63 07 fb 48 85 db 74 16 48 89 df c6 07 00 66 66 66 90 31 c0 5b c3 <80> 24 25 07 00 00 00 fb 31 c0 5b c3 b8 f0 ff ff ff 5b c3 66 0f 1f > [ 5758.234478] RSP: 0018:ffffb147442d7af0 EFLAGS: 00010246 > [ 5758.240309] RAX: 0000000000000000 RBX: 000000000014b217 RCX: ffffb14779fd9000 > [ 5758.248281] RDX: 000000000014b217 RSI: ffff9c52f2ab1400 RDI: 000000000014b217 > [ 5758.256246] RBP: ffffe00c51168080 R08: ffffe00c5116fe08 R09: ffff9c52fffd3000 > [ 5758.264208] R10: ffffe00c511537c8 R11: ffff9c52fffd3c90 R12: 0000000000000000 > [ 5758.272172] R13: ffffe00c51170000 R14: ffffe00c51170000 R15: ffffe00c51168040 > [ 5758.280134] FS: 0000000000000000(0000) GS:ffff9c52f2a80000(0000) knlGS:0000000000000000 > [ 5758.289163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 5758.295575] CR2: 0000000000000007 CR3: 0000000022a0e003 CR4: 00000000000606e0 > [ 5758.303538] Call Trace: > [ 5758.306273] split_huge_page_to_list+0x88b/0x950 > [ 5758.311433] deferred_split_scan+0x1ca/0x310 > [ 5758.316202] do_shrink_slab+0x12c/0x2a0 > [ 5758.320491] shrink_slab+0x20f/0x2c0 > [ 5758.324482] shrink_node+0x240/0x6c0 > [ 5758.328469] balance_pgdat+0x2d1/0x550 > [ 5758.332652] kswapd+0x201/0x3c0 > [ 5758.336157] ? finish_wait+0x80/0x80 > [ 5758.340147] ? balance_pgdat+0x550/0x550 > [ 5758.344525] kthread+0x114/0x130 > [ 5758.348126] ? kthread_park+0x80/0x80 > [ 5758.352214] ret_from_fork+0x22/0x30 > [ 5758.356203] Modules linked in: fuse zram rfkill sunrpc intel_rapl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp mgag200 iTCO_wdt crct10dif_pclmul iTCO_vendor_support drm_kms_helper crc32_pclmul ghash_clmulni_intel syscopyarea sysfillrect sysimgblt fb_sys_fops cec rapl joydev intel_cstate ipmi_si ipmi_devintf drm intel_uncore i2c_i801 ipmi_msghandler pcspkr lpc_ich mei_me i2c_smbus mei ioatdma ip_tables xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg igb ahci libahci i2c_algo_bit crc32c_intel libata dca wmi dm_mirror dm_region_hash dm_log dm_mod > [ 5758.412673] CR2: 0000000000000007 > [ 0.000000] Linux version 5.9.0-0.rc3.1.tst.el8.x86_64 (mockbuild@x86-vm-15.build.eng.bos.redhat.com) (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #1 SMP Wed Sep 9 16:03:34 EDT 2020 > > After further digging it's found that the following race condition exists in the > original implementation, > > CPU1 CPU2 > ---- ---- > deferred_split_scan() > split_huge_page(page) /* page isn't compound head */ > split_huge_page_to_list(page, NULL) > __split_huge_page(page, ) > ClearPageCompound(head) > /* unlock all subpages except page (not head) */ > add_to_swap(head) /* not THP */ > get_swap_page(head) > add_to_swap_cache(head, ) > SetPageSwapCache(head) > if PageSwapCache(head) > split_swap_cluster(/* swap entry of head */) > /* Deref sis->cluster_info: NULL accessing! */ > > So, in split_huge_page_to_list(), PageSwapCache() is called for the already > split and unlocked "head", which may be added to swap cache in another CPU. So > split_swap_cluster() may be called wrongly. > > To fix the race, the call to split_swap_cluster() is moved to > __split_huge_page() before all subpages are unlocked. So that the > PageSwapCache() is stable. > > Fixes: 59807685a7e77 ("mm, THP, swap: support splitting THP for THP swap out") > Reported-and-tested-by: Rafael Aquini > Signed-off-by: "Huang, Ying" > Cc: Hugh Dickins > Cc: Kirill A. Shutemov > Cc: Andrea Arcangeli Looks good to me. Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov