Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759938AbcDJTEP (ORCPT ); Sun, 10 Apr 2016 15:04:15 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:53711 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759561AbcDJTEL (ORCPT ); Sun, 10 Apr 2016 15:04:11 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Andrew Cooper , Andy Lutomirski , Boris Ostrovsky , Borislav Petkov , Brian Gerst , David Vrabel , Denys Vlasenko , "H. Peter Anvin" , Jan Beulich , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.4 036/210] x86/iopl: Fix iopl capability check on Xen PV Date: Sun, 10 Apr 2016 11:34:17 -0700 Message-Id: <20160410183527.944075406@linuxfoundation.org> X-Mailer: git-send-email 2.8.0 In-Reply-To: <20160410183526.651820045@linuxfoundation.org> References: <20160410183526.651820045@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2152 Lines: 64 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit c29016cf41fe9fa994a5ecca607cf5f1cd98801e upstream. iopl(3) is supposed to work if iopl is already 3, even if unprivileged. This didn't work right on Xen PV. Fix it. Reviewewd-by: Jan Beulich Signed-off-by: Andy Lutomirski Cc: Andrew Cooper Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: David Vrabel Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jan Beulich Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/8ce12013e6e4c0a44a97e316be4a6faff31bd5ea.1458162709.git.luto@kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/ioport.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -96,9 +96,14 @@ asmlinkage long sys_ioperm(unsigned long 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, leve 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;