From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757895AbaCRVbS (ORCPT ); Tue, 18 Mar 2014 17:31:18 -0400 Received: from terminus.zytor.com ([198.137.202.10]:54531 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933749AbaCRVaQ (ORCPT ); Tue, 18 Mar 2014 17:30:16 -0400 Date: Tue, 18 Mar 2014 14:29:45 -0700 From: tip-bot for Andy Lutomirski Message-ID: Cc: linux-kernel@vger.kernel.org, luto@amacapital.net, hpa@zytor.com, mingo@kernel.org, stefani@seibold.net, tglx@linutronix.de, hpa@linux.intel.com Reply-To: mingo@kernel.org, hpa@zytor.com, luto@amacapital.net, linux-kernel@vger.kernel.org, stefani@seibold.net, tglx@linutronix.de, hpa@linux.intel.com In-Reply-To: <1395094933-14252-12-git-send-email-stefani@seibold.net> References: <1395094933-14252-12-git-send-email-stefani@seibold.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/vdso] x86, vdso: Zero-pad the VVAR page Git-Commit-ID: 309944be296efbb3ca4737d12ef49d2ba97cbecc 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 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 309944be296efbb3ca4737d12ef49d2ba97cbecc Gitweb: http://git.kernel.org/tip/309944be296efbb3ca4737d12ef49d2ba97cbecc Author: Andy Lutomirski AuthorDate: Mon, 17 Mar 2014 23:22:11 +0100 Committer: H. Peter Anvin CommitDate: Tue, 18 Mar 2014 12:52:44 -0700 x86, vdso: Zero-pad the VVAR page By coincidence, the VVAR page is at the end of an ELF segment. As a result, if it ends up being a partial page, the kernel loader will leave garbage behind at the end of the vvar page. Zero-pad it to a full page to fix this issue. This has probably been broken since the VVAR page was introduced. On QEMU, if you dump the run-time contents of the VVAR page, you can find entertaining strings from seabios left behind. It's remotely possible that this is a security bug -- conceivably there's some BIOS out there that leaves something sensitive in the few K of memory that is exposed to userspace. Signed-off-by: Stefani Seibold Link: http://lkml.kernel.org/r/1395094933-14252-12-git-send-email-stefani@seibold.net Signed-off-by: H. Peter Anvin --- arch/x86/kernel/vmlinux.lds.S | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 1d4897b..49edf2d 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -164,6 +164,11 @@ SECTIONS #undef __VVAR_KERNEL_LDS #undef EMIT_VVAR + /* + * Pad the rest of the page with zeros. Otherwise the loader + * can leave garbage here. + */ + . = __vvar_beginning_hack + PAGE_SIZE; } :data . = ALIGN(__vvar_page + PAGE_SIZE, PAGE_SIZE);