From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 8BD326B0009 for ; Wed, 2 May 2018 14:27:44 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id t74-v6so3252102pgc.14 for ; Wed, 02 May 2018 11:27:44 -0700 (PDT) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id t184si12317006pfb.98.2018.05.02.11.27.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 02 May 2018 11:27:43 -0700 (PDT) Subject: Patch "x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init" has been added to the 4.9-stable tree From: Date: Wed, 02 May 2018 11:16:55 -0700 Message-ID: <1525285015209214@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: 20180406205514.8D898241@viggo.jf.intel.com, aarcange@redhat.com, alexander.levin@microsoft.com, arjan@linux.intel.com, bp@alien8.de, dan.j.williams@intel.com, dave.hansen@linux.intel.com, dwmw2@infradead.org, gregkh@linuxfoundation.org, hughd@google.com, jgross@suse.com, jpoimboe@redhat.com, keescook@chromium.org, linux-mm@kvack.org, luto@kernel.org, mingo@kernel.org, namit@vmware.com, peterz@infradead.org, tglx@linutronix.de, torvalds@linux-foundation.org Cc: stable-commits@vger.kernel.org This is a note to let you know that I've just added the patch titled x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-mm-do-not-forbid-_page_rw-before-init-for-__ro_after_init.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Wed May 2 10:53:11 PDT 2018 From: Dave Hansen Date: Fri, 6 Apr 2018 13:55:14 -0700 Subject: x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init From: Dave Hansen [ Upstream commit 639d6aafe437a7464399d2a77d006049053df06f ] __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 Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/pageattr.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -279,9 +279,11 @@ static inline pgprot_t static_protection /* * 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; Patches currently in stable-queue which might be from dave.hansen@linux.intel.com are queue-4.9/x86-mm-do-not-forbid-_page_rw-before-init-for-__ro_after_init.patch