From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:51772 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388233AbeHNUNo (ORCPT ); Tue, 14 Aug 2018 16:13:44 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andi Kleen , Thomas Gleixner , Josh Poimboeuf , Dave Hansen Subject: [PATCH 4.18 09/79] x86/speculation/l1tf: Make sure the first page is always reserved Date: Tue, 14 Aug 2018 19:16:28 +0200 Message-Id: <20180814171337.159130282@linuxfoundation.org> In-Reply-To: <20180814171336.799314117@linuxfoundation.org> References: <20180814171336.799314117@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andi Kleen The L1TF workaround doesn't make any attempt to mitigate speculate accesses to the first physical page for zeroed PTEs. Normally it only contains some data from the early real mode BIOS. It's not entirely clear that the first page is reserved in all configurations, so add an extra reservation call to make sure it is really reserved. In most configurations (e.g. with the standard reservations) it's likely a nop. Signed-off-by: Andi Kleen Signed-off-by: Thomas Gleixner Reviewed-by: Josh Poimboeuf Acked-by: Dave Hansen Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/setup.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -823,6 +823,12 @@ void __init setup_arch(char **cmdline_p) memblock_reserve(__pa_symbol(_text), (unsigned long)__bss_stop - (unsigned long)_text); + /* + * Make sure page 0 is always reserved because on systems with + * L1TF its contents can be leaked to user processes. + */ + memblock_reserve(0, PAGE_SIZE); + early_reserve_initrd(); /*