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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 D0C69C43457 for ; Fri, 9 Oct 2020 07:37:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6AF2222266 for ; Fri, 9 Oct 2020 07:37:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6AF2222266 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E5C996B006C; Fri, 9 Oct 2020 03:37:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E0B816B006E; Fri, 9 Oct 2020 03:37:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CD3B96B0070; Fri, 9 Oct 2020 03:37:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0068.hostedemail.com [216.40.44.68]) by kanga.kvack.org (Postfix) with ESMTP id A1CF86B006C for ; Fri, 9 Oct 2020 03:37:08 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 4B1711EE6 for ; Fri, 9 Oct 2020 07:37:08 +0000 (UTC) X-FDA: 77351580936.27.doll00_51007ec271de Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin27.hostedemail.com (Postfix) with ESMTP id 2C60C3D668 for ; Fri, 9 Oct 2020 07:37:08 +0000 (UTC) X-HE-Tag: doll00_51007ec271de X-Filterd-Recvd-Size: 7336 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf21.hostedemail.com (Postfix) with ESMTP for ; Fri, 9 Oct 2020 07:37:06 +0000 (UTC) IronPort-SDR: nRWDOVRy3vR3IEUsdofX5Tu1+PUOwBYe0qlKhaAbhXYXEdyYCqW6fktJEvs9e3S0Bn05nSWhRP 8OqyRw7sK3PA== X-IronPort-AV: E=McAfee;i="6000,8403,9768"; a="250148730" X-IronPort-AV: E=Sophos;i="5.77,354,1596524400"; d="scan'208";a="250148730" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Oct 2020 00:37:04 -0700 IronPort-SDR: MDJhdq95lbtKuXRxTvEgaUWRva3ZXx9xfAoO4FRwSYRuqtqbEihOfXNaSkAy/f7xelLYyPSwUb 2G1M/URwmWjg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,354,1596524400"; d="scan'208";a="518580128" Received: from yhuang-dev.sh.intel.com ([10.239.159.65]) by fmsmga006.fm.intel.com with ESMTP; 09 Oct 2020 00:37:01 -0700 From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Rafael Aquini , Hugh Dickins , "Kirill A . Shutemov" , Andrea Arcangeli Subject: [PATCH] mm: Fix a race during split THP Date: Fri, 9 Oct 2020 15:36:47 +0800 Message-Id: <20201009073647.1531083-1-ying.huang@intel.com> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 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: 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: 00000000000= 00007 [ 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 SE5= C600.86B.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 6= a 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: ffffb1477= 9fd9000 [ 5758.248281] RDX: 000000000014b217 RSI: ffff9c52f2ab1400 RDI: 000000000= 014b217 [ 5758.256246] RBP: ffffe00c51168080 R08: ffffe00c5116fe08 R09: ffff9c52f= ffd3000 [ 5758.264208] R10: ffffe00c511537c8 R11: ffff9c52fffd3c90 R12: 000000000= 0000000 [ 5758.272172] R13: ffffe00c51170000 R14: ffffe00c51170000 R15: ffffe00c5= 1168040 [ 5758.280134] FS: 0000000000000000(0000) GS:ffff9c52f2a80000(0000) knlG= S:0000000000000000 [ 5758.289163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 5758.295575] CR2: 0000000000000007 CR3: 0000000022a0e003 CR4: 000000000= 00606e0 [ 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 crc3= 2_pclmul ghash_clmulni_intel syscopyarea sysfillrect sysimgblt fb_sys_fop= s 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_table= s xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg igb ahci libahci i2c_algo_b= it 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_s= wap(head) /* not THP */ get_sw= ap_page(head) add_to= _swap_cache(head, ) SetP= ageSwapCache(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 alrea= dy split and unlocked "head", which may be added to swap cache in another CP= U. 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 --- mm/huge_memory.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index cba3812a5c3e..87b0389673dd 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2478,6 +2478,12 @@ static void __split_huge_page(struct page *page, s= truct list_head *list, =20 remap_page(head, nr); =20 + if (PageSwapCache(head)) { + swp_entry_t entry =3D { .val =3D page_private(head) }; + + split_swap_cluster(entry); + } + for (i =3D 0; i < nr; i++) { struct page *subpage =3D head + i; if (subpage =3D=3D page) @@ -2713,12 +2719,7 @@ int split_huge_page_to_list(struct page *page, str= uct list_head *list) } =20 __split_huge_page(page, list, end, flags); - if (PageSwapCache(head)) { - swp_entry_t entry =3D { .val =3D page_private(head) }; - - ret =3D split_swap_cluster(entry); - } else - ret =3D 0; + ret =3D 0; } else { if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { pr_alert("total_mapcount: %u, page_count(): %u\n", --=20 2.28.0