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[209.132.180.67]) by mx.google.com with ESMTP id d15-v6si713696pls.232.2018.04.09.10.20.31; Mon, 09 Apr 2018 10:21:09 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754008AbeDIRQL (ORCPT + 99 others); Mon, 9 Apr 2018 13:16:11 -0400 Received: from terminus.zytor.com ([198.137.202.136]:60649 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753530AbeDIRQK (ORCPT ); Mon, 9 Apr 2018 13:16:10 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTP id w39HF9HQ1894661; Mon, 9 Apr 2018 10:15:09 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w39HF9PS1894655; Mon, 9 Apr 2018 10:15:09 -0700 Date: Mon, 9 Apr 2018 10:15:09 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Dave Hansen Message-ID: Cc: luto@kernel.org, gregkh@linuxfoundation.org, namit@vmware.com, hpa@zytor.com, dan.j.williams@intel.com, dave.hansen@linux.intel.com, tglx@linutronix.de, dwmw2@infradead.org, torvalds@linux-foundation.org, hughd@google.com, arjan@linux.intel.com, keescook@chromium.org, aarcange@redhat.com, mingo@kernel.org, bp@alien8.de, linux-kernel@vger.kernel.org, jpoimboe@redhat.com, jgross@suse.com, peterz@infradead.org Reply-To: dan.j.williams@intel.com, dave.hansen@linux.intel.com, torvalds@linux-foundation.org, dwmw2@infradead.org, tglx@linutronix.de, luto@kernel.org, hpa@zytor.com, gregkh@linuxfoundation.org, namit@vmware.com, aarcange@redhat.com, keescook@chromium.org, mingo@kernel.org, hughd@google.com, arjan@linux.intel.com, jpoimboe@redhat.com, linux-kernel@vger.kernel.org, bp@alien8.de, jgross@suse.com, peterz@infradead.org In-Reply-To: <20180406205514.8D898241@viggo.jf.intel.com> References: <20180406205514.8D898241@viggo.jf.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/pti] x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init Git-Commit-ID: efad2b4151521c944e405272035a673c74125c65 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on terminus.zytor.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: efad2b4151521c944e405272035a673c74125c65 Gitweb: https://git.kernel.org/tip/efad2b4151521c944e405272035a673c74125c65 Author: Dave Hansen AuthorDate: Fri, 6 Apr 2018 13:55:14 -0700 Committer: Ingo Molnar CommitDate: Mon, 9 Apr 2018 18:27:34 +0200 x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init __ro_after_init data gets stuck in the .rodata section. That's normally fine because the kernel itself manages the R/W properties. But, if we run __change_page_attr() on an area which is __ro_after_init, the .rodata checks will trigger and force the area to be immediately read-only, even if it is early-ish in boot. This caused problems when trying to clear the _PAGE_GLOBAL bit for these area in the PTI code: it cleared _PAGE_GLOBAL like I asked, but also took it up on itself to clear _PAGE_RW. The kernel then oopses the next time it wrote to a __ro_after_init data structure. To fix this, add the kernel_set_to_readonly check, just like we have for kernel text, just a few lines below in this function. Signed-off-by: Dave Hansen Acked-by: Kees Cook Cc: Andrea Arcangeli Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Dan Williams Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: Hugh Dickins Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Nadav Amit Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180406205514.8D898241@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/mm/pageattr.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 968f51a2e39b..a7324045d87d 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -298,9 +298,11 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address, /* * The .rodata section needs to be read-only. Using the pfn - * catches all aliases. + * catches all aliases. This also includes __ro_after_init, + * so do not enforce until kernel_set_to_readonly is true. */ - if (within(pfn, __pa_symbol(__start_rodata) >> PAGE_SHIFT, + if (kernel_set_to_readonly && + within(pfn, __pa_symbol(__start_rodata) >> PAGE_SHIFT, __pa_symbol(__end_rodata) >> PAGE_SHIFT)) pgprot_val(forbidden) |= _PAGE_RW;