From patchwork Mon Aug 30 23:59:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Edgecombe, Rick P" X-Patchwork-Id: 12466137 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 6840DC4320A for ; Tue, 31 Aug 2021 00:00:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0386361027 for ; Tue, 31 Aug 2021 00:00:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 0386361027 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id B869C900003; Mon, 30 Aug 2021 20:00:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A6CB4940008; Mon, 30 Aug 2021 20:00:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F167900003; Mon, 30 Aug 2021 20:00:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0249.hostedemail.com [216.40.44.249]) by kanga.kvack.org (Postfix) with ESMTP id 52F8C900004 for ; Mon, 30 Aug 2021 20:00:01 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 16E2525714 for ; Tue, 31 Aug 2021 00:00:01 +0000 (UTC) X-FDA: 78533417802.17.188C35B Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by imf14.hostedemail.com (Postfix) with ESMTP id 8ABEF6001988 for ; Tue, 31 Aug 2021 00:00:00 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10092"; a="205504321" X-IronPort-AV: E=Sophos;i="5.84,364,1620716400"; d="scan'208";a="205504321" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Aug 2021 17:00:00 -0700 X-IronPort-AV: E=Sophos;i="5.84,364,1620716400"; d="scan'208";a="530712816" Received: from ajinkyak-mobl2.amr.corp.intel.com (HELO rpedgeco-desk.amr.corp.intel.com) ([10.212.240.95]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Aug 2021 16:59:59 -0700 From: Rick Edgecombe To: dave.hansen@intel.com, luto@kernel.org, peterz@infradead.org, x86@kernel.org, akpm@linux-foundation.org, keescook@chromium.org, shakeelb@google.com, vbabka@suse.cz, rppt@kernel.org Cc: Rick Edgecombe , linux-mm@kvack.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com, ira.weiny@intel.com, dan.j.williams@intel.com, linux-kernel@vger.kernel.org Subject: [RFC PATCH v2 04/19] mm: Explicitly zero page table lock ptr Date: Mon, 30 Aug 2021 16:59:12 -0700 Message-Id: <20210830235927.6443-5-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210830235927.6443-1-rick.p.edgecombe@intel.com> References: <20210830235927.6443-1-rick.p.edgecombe@intel.com> Authentication-Results: imf14.hostedemail.com; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=intel.com (policy=none); spf=none (imf14.hostedemail.com: domain of rick.p.edgecombe@intel.com has no SPF policy when checking 134.134.136.126) smtp.mailfrom=rick.p.edgecombe@intel.com X-Stat-Signature: hd8gk7yiwki8i18t3iaw476pdjr1oh5c X-Rspamd-Queue-Id: 8ABEF6001988 X-Rspamd-Server: rspam04 X-HE-Tag: 1630368000-326275 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: In ptlock_init() there is a VM_BUG_ON_PAGE() check on the page table lock pointer. Explicitly zero the lock in ptlock_free() so a page table lock can be re-initialized without triggering the BUG_ON(). It appears this doesn't normally trigger because the private field shares the same space in struct page as ptl and page tables always return to the buddy allocator before being re-initialized as new page tables. When the page returns to the buddy allocator, private gets used to store the page order, so it inadvertently clears ptl as well. In future patches, pages will get re-initialized as page tables without returning to the buddy allocator so this is needed. Signed-off-by: Rick Edgecombe --- mm/memory.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/memory.c b/mm/memory.c index 25fc46e87214..e6d630463c7f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5465,5 +5465,6 @@ bool ptlock_alloc(struct page *page) void ptlock_free(struct page *page) { kmem_cache_free(page_ptl_cachep, page->ptl); + page->ptl = 0; } #endif