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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 B648FC4321D for ; Thu, 23 Aug 2018 09:11:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 78432208EC for ; Thu, 23 Aug 2018 09:11:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 78432208EC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org 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 S2389199AbeHWMkM (ORCPT ); Thu, 23 Aug 2018 08:40:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:56996 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727875AbeHWMkM (ORCPT ); Thu, 23 Aug 2018 08:40:12 -0400 Received: from localhost (5355525A.cm-6-6b.dynamic.ziggo.nl [83.85.82.90]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 5D80AC9E; Thu, 23 Aug 2018 09:11:26 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dave Hansen , Thomas Gleixner , keescook@google.com, aarcange@redhat.com, jgross@suse.com, jpoimboe@redhat.com, peterz@infradead.org, hughd@google.com, torvalds@linux-foundation.org, bp@alien8.de, luto@kernel.org, ak@linux.intel.com Subject: [PATCH 4.18 03/22] mm: Allow non-direct-map arguments to free_reserved_area() Date: Thu, 23 Aug 2018 09:56:29 +0200 Message-Id: <20180823074759.411355212@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180823074759.234685844@linuxfoundation.org> References: <20180823074759.234685844@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dave Hansen commit 0d83432811f26871295a9bc24d3c387924da6071 upstream. 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 not highmem pages for which virt_to_page() would fail. Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Cc: keescook@google.com Cc: aarcange@redhat.com Cc: jgross@suse.com Cc: jpoimboe@redhat.com Cc: gregkh@linuxfoundation.org Cc: peterz@infradead.org Cc: hughd@google.com Cc: torvalds@linux-foundation.org Cc: bp@alien8.de Cc: luto@kernel.org Cc: ak@linux.intel.com Cc: Kees Cook 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 Link: https://lkml.kernel.org/r/20180802225826.1287AE3E@viggo.jf.intel.com Signed-off-by: Greg Kroah-Hartman --- mm/page_alloc.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -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)