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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 5927FC43142 for ; Thu, 2 Aug 2018 22:59:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18B6D21571 for ; Thu, 2 Aug 2018 22:59:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18B6D21571 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732111AbeHCAvy (ORCPT ); Thu, 2 Aug 2018 20:51:54 -0400 Received: from mga12.intel.com ([192.55.52.136]:37019 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731697AbeHCAvx (ORCPT ); Thu, 2 Aug 2018 20:51:53 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Aug 2018 15:58:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,437,1526367600"; d="scan'208";a="61641442" Received: from viggo.jf.intel.com (HELO localhost.localdomain) ([10.54.77.144]) by orsmga007.jf.intel.com with ESMTP; 02 Aug 2018 15:58:35 -0700 Subject: [PATCH 2/7] mm: allow non-direct-map arguments to free_reserved_area() To: linux-kernel@vger.kernel.org Cc: Dave Hansen , keescook@google.com, tglx@linutronix.de, mingo@kernel.org, aarcange@redhat.com, jgross@suse.com, jpoimboe@redhat.com, gregkh@linuxfoundation.org, peterz@infradead.org, hughd@google.com, torvalds@linux-foundation.org, bp@alien8.de, luto@kernel.org, ak@linux.intel.com From: Dave Hansen Date: Thu, 02 Aug 2018 15:58:26 -0700 References: <20180802225823.4711C55B@viggo.jf.intel.com> In-Reply-To: <20180802225823.4711C55B@viggo.jf.intel.com> Message-Id: <20180802225826.1287AE3E@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen free_reserved_area() takes pointers as arguments to show which addresses should be freed. However, it does this in a somewhat ambiguous way. If it gets a kernel direct map address, it always works. However, if it gets an address that is part of the kernel image alias mapping, it can fail. It fails if all of the following happen: * The specified address is part of the kernel image alias * Poisoning is requested (forcing a memset()) * The address is in a read-only portion of the kernel image The memset() fails on the read-only mapping, of course. free_reserved_area() *is* called both on the direct map and on kernel image alias addresses. We've just lucked out thus far that the kernel image alias areas it gets used on are read-write. I'm fairly sure this has been just a happy accident. It is quite easy to make free_reserved_area() work for all cases: just convert the address to a direct map address before doing the memset(), and do this unconditionally. There is little chance of a regression here because we previously did a virt_to_page() on the address for the memset, so we know these are no highmem pages for which virt_to_page() would fail. Signed-off-by: Dave Hansen Cc: Kees Cook Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Andrea Arcangeli Cc: Juergen Gross Cc: Josh Poimboeuf Cc: Greg Kroah-Hartman Cc: Peter Zijlstra Cc: Hugh Dickins Cc: Linus Torvalds Cc: Borislav Petkov Cc: Andy Lutomirski Cc: Andi Kleen --- b/mm/page_alloc.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff -puN mm/page_alloc.c~x86-mm-init-handle-non-linear-map-ranges-free_init_pages mm/page_alloc.c --- a/mm/page_alloc.c~x86-mm-init-handle-non-linear-map-ranges-free_init_pages 2018-08-02 14:14:47.860483278 -0700 +++ b/mm/page_alloc.c 2018-08-02 14:14:47.865483278 -0700 @@ -6939,9 +6939,21 @@ unsigned long free_reserved_area(void *s start = (void *)PAGE_ALIGN((unsigned long)start); end = (void *)((unsigned long)end & PAGE_MASK); for (pos = start; pos < end; pos += PAGE_SIZE, pages++) { + struct page *page = virt_to_page(pos); + void *direct_map_addr; + + /* + * 'direct_map_addr' might be different from 'pos' + * because some architectures' virt_to_page() + * work with aliases. Getting the direct map + * address ensures that we get a _writeable_ + * alias for the memset(). + */ + direct_map_addr = page_address(page); if ((unsigned int)poison <= 0xFF) - memset(pos, poison, PAGE_SIZE); - free_reserved_page(virt_to_page(pos)); + memset(direct_map_addr, poison, PAGE_SIZE); + + free_reserved_page(page); } if (pages && s) _