From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753521AbaCQW3E (ORCPT ); Mon, 17 Mar 2014 18:29:04 -0400 Received: from www84.your-server.de ([213.133.104.84]:39208 "EHLO www84.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753081AbaCQW3B (ORCPT ); Mon, 17 Mar 2014 18:29:01 -0400 From: Stefani Seibold To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, ak@linux.intel.com, aarcange@redhat.com, john.stultz@linaro.org, luto@amacapital.net, xemul@parallels.com, gorcunov@openvz.org, andriy.shevchenko@linux.intel.com Cc: Martin.Runge@rohde-schwarz.com, Andreas.Brief@rohde-schwarz.com, stefani@seibold.net Subject: [PATCH v23 11/13] x86, vdso: Zero-pad the VVAR page Date: Mon, 17 Mar 2014 23:22:11 +0100 Message-Id: <1395094933-14252-12-git-send-email-stefani@seibold.net> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1395094933-14252-1-git-send-email-stefani@seibold.net> References: <1395094933-14252-1-git-send-email-stefani@seibold.net> X-Authenticated-Sender: stefani@seibold.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski 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 --- 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); -- 1.9.0