Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757139AbcDJUvd (ORCPT ); Sun, 10 Apr 2016 16:51:33 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:51598 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756332AbcDJShy (ORCPT ); Sun, 10 Apr 2016 14:37:54 -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 4.5 030/238] x86/iopl/64: Properly context-switch IOPL on Xen PV Date: Sun, 10 Apr 2016 11:33:27 -0700 Message-Id: <20160410183458.182915019@linuxfoundation.org> X-Mailer: git-send-email 2.8.0 In-Reply-To: <20160410183456.398741366@linuxfoundation.org> References: <20160410183456.398741366@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: 3062 Lines: 92 4.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit b7a584598aea7ca73140cb87b40319944dd3393f upstream. On Xen PV, regs->flags doesn't reliably reflect IOPL and the exit-to-userspace code doesn't change IOPL. We need to context switch it manually. I'm doing this without going through paravirt because this is specific to Xen PV. After the dust settles, we can merge this with the 32-bit code, tidy up the iopl syscall implementation, and remove the set_iopl pvop entirely. Fixes XSA-171. 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/693c3bd7aeb4d3c27c92c622b7d0f554a458173c.1458162709.git.luto@kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/xen/hypervisor.h | 2 ++ arch/x86/kernel/process_64.c | 12 ++++++++++++ arch/x86/xen/enlighten.c | 2 +- 3 files changed, 15 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/xen/hypervisor.h +++ b/arch/x86/include/asm/xen/hypervisor.h @@ -62,4 +62,6 @@ void xen_arch_register_cpu(int num); void xen_arch_unregister_cpu(int num); #endif +extern void xen_set_iopl_mask(unsigned mask); + #endif /* _ASM_X86_XEN_HYPERVISOR_H */ --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -48,6 +48,7 @@ #include #include #include +#include asmlinkage extern void ret_from_fork(void); @@ -411,6 +412,17 @@ __switch_to(struct task_struct *prev_p, task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV)) __switch_to_xtra(prev_p, next_p, tss); +#ifdef CONFIG_XEN + /* + * On Xen PV, IOPL bits in pt_regs->flags have no effect, and + * current_pt_regs()->flags may not match the current task's + * intended IOPL. We need to switch it manually. + */ + if (unlikely(static_cpu_has(X86_FEATURE_XENPV) && + prev->iopl != next->iopl)) + xen_set_iopl_mask(next->iopl); +#endif + if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) { /* * AMD CPUs have a misfeature: SYSRET sets the SS selector but --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -961,7 +961,7 @@ static void xen_load_sp0(struct tss_stru tss->x86_tss.sp0 = thread->sp0; } -static void xen_set_iopl_mask(unsigned mask) +void xen_set_iopl_mask(unsigned mask) { struct physdev_set_iopl set_iopl;