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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1EF8C433FE for ; Sat, 26 Feb 2022 09:41:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0A7718D0002; Sat, 26 Feb 2022 04:41:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 057588D0001; Sat, 26 Feb 2022 04:41:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E88E88D0002; Sat, 26 Feb 2022 04:41:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0119.hostedemail.com [216.40.44.119]) by kanga.kvack.org (Postfix) with ESMTP id D66D38D0001 for ; Sat, 26 Feb 2022 04:41:26 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 470C08249980 for ; Sat, 26 Feb 2022 09:41:26 +0000 (UTC) X-FDA: 79184438172.19.2F28B3B Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf21.hostedemail.com (Postfix) with ESMTP id 13D191C0002 for ; Sat, 26 Feb 2022 09:41:23 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4K5M3d3Fy3z1FDWQ; Sat, 26 Feb 2022 17:36:45 +0800 (CST) Received: from huawei.com (10.175.124.27) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Sat, 26 Feb 2022 17:41:19 +0800 From: Miaohe Lin To: , , , CC: , , Subject: [PATCH RFC] mm/memory-failure.c: fix memory failure race with memory offline Date: Sat, 26 Feb 2022 17:40:34 +0800 Message-ID: <20220226094034.23938-1-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 13D191C0002 X-Stat-Signature: djeak88zopbot8ihg9fyj1fxzsm9wi5t Authentication-Results: imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-HE-Tag: 1645868483-972617 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: There is a theoretical race window between memory failure and memory offline. Think about the below scene: CPU A CPU B memory_failure offline_pages mutex_lock(&mf_mutex); TestSetPageHWPoison(p) start_isolate_page_range has_unmovable_pages --PageHWPoison is movable do { scan_movable_pages do_migrate_range --PageHWPoison isn't migrated } test_pages_isolated --PageHWPoison is isolated remove_memory access page... bang ... When PageHWPoison is set, the page could be offlined anytime regardless of the page refcnt. It's bacause start_isolate_page_range treats HWPoison page as movable and already isolated, so the page range can be successful= ly isolated. soft_offline_page and unpoison_memory have the similar race. Fi= x this by using get_online_mems + put_online_mems pair to guard aginst memo= ry offline when doing memory failure. There is a even worse race window. If the page refcnt is held, then memor= y failure happens, the page could be offlined while it's still in use. So T= he assumption that a page can not be offlined when the page refcnt is held i= s now broken. This theoretical race window could happen in every vm activit= y. But this race window might be too small to fix. Signed-off-by: Miaohe Lin --- mm/memory-failure.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 5444a8ef4867..b85232a64104 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1702,6 +1702,7 @@ int memory_failure(unsigned long pfn, int flags) if (!sysctl_memory_failure_recovery) panic("Memory failure on page %lx", pfn); =20 + get_online_mems(); mutex_lock(&mf_mutex); =20 p =3D pfn_to_online_page(pfn); @@ -1894,11 +1895,13 @@ int memory_failure(unsigned long pfn, int flags) identify_page_state: res =3D identify_page_state(pfn, p, page_flags); mutex_unlock(&mf_mutex); + put_online_mems(); return res; unlock_page: unlock_page(p); unlock_mutex: mutex_unlock(&mf_mutex); + put_online_mems(); return res; } EXPORT_SYMBOL_GPL(memory_failure); @@ -2058,6 +2061,7 @@ int unpoison_memory(unsigned long pfn) if (!pfn_valid(pfn)) return -ENXIO; =20 + get_online_mems(); p =3D pfn_to_page(pfn); page =3D compound_head(p); =20 @@ -2114,6 +2118,7 @@ int unpoison_memory(unsigned long pfn) =20 unlock_mutex: mutex_unlock(&mf_mutex); + put_online_mems(); return ret; } EXPORT_SYMBOL(unpoison_memory); @@ -2278,10 +2283,12 @@ int soft_offline_page(unsigned long pfn, int flag= s) if (flags & MF_COUNT_INCREASED) ref_page =3D pfn_to_page(pfn); =20 + get_online_mems(); /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */ page =3D pfn_to_online_page(pfn); if (!page) { put_ref_page(ref_page); + put_online_mems(); return -EIO; } =20 @@ -2291,13 +2298,12 @@ int soft_offline_page(unsigned long pfn, int flag= s) pr_info("%s: %#lx page already poisoned\n", __func__, pfn); put_ref_page(ref_page); mutex_unlock(&mf_mutex); + put_online_mems(); return 0; } =20 retry: - get_online_mems(); ret =3D get_hwpoison_page(page, flags); - put_online_mems(); =20 if (ret > 0) { ret =3D soft_offline_in_use_page(page); @@ -2310,6 +2316,7 @@ int soft_offline_page(unsigned long pfn, int flags) } =20 mutex_unlock(&mf_mutex); + put_online_mems(); =20 return ret; } --=20 2.23.0