From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935180AbcCPVOj (ORCPT ); Wed, 16 Mar 2016 17:14:39 -0400 Received: from mail.kernel.org ([198.145.29.136]:37934 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755715AbcCPVOc (ORCPT ); Wed, 16 Mar 2016 17:14:32 -0400 From: Andy Lutomirski To: x86@kernel.org, Andrew Cooper , Jan Beulich Cc: Borislav Petkov , David Vrabel , Boris Ostrovsky , linux-kernel@vger.kernel.org, Andy Lutomirski , stable@vger.kernel.org Subject: [PATCH v4 3/3] x86/iopl: Fix iopl capability check on Xen PV Date: Wed, 16 Mar 2016 14:14:22 -0700 Message-Id: <8ce12013e6e4c0a44a97e316be4a6faff31bd5ea.1458162709.git.luto@kernel.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org iopl(3) is supposed to work if iopl is already 3, even if unprivileged. This didn't work right on Xen PV. Fix it. Cc: stable@vger.kernel.org Reviewewd-by: Jan Beulich Signed-off-by: Andy Lutomirski --- arch/x86/kernel/ioport.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c index 37dae792dbbe..589b3193f102 100644 --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -96,9 +96,14 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) SYSCALL_DEFINE1(iopl, unsigned int, level) { struct pt_regs *regs = current_pt_regs(); - unsigned int old = (regs->flags >> 12) & 3; struct thread_struct *t = ¤t->thread; + /* + * Careful: the IOPL bits in regs->flags are undefined under Xen PV + * and changing them has no effect. + */ + unsigned int old = t->iopl >> X86_EFLAGS_IOPL_BIT; + if (level > 3) return -EINVAL; /* Trying to gain more privileges? */ @@ -106,8 +111,9 @@ SYSCALL_DEFINE1(iopl, unsigned int, level) if (!capable(CAP_SYS_RAWIO)) return -EPERM; } - regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12); - t->iopl = level << 12; + regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | + (level << X86_EFLAGS_IOPL_BIT); + t->iopl = level << X86_EFLAGS_IOPL_BIT; set_iopl_mask(t->iopl); return 0; -- 2.5.0