From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753390AbeA3WjY (ORCPT ); Tue, 30 Jan 2018 17:39:24 -0500 Received: from terminus.zytor.com ([65.50.211.136]:48695 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752510AbeA3WjU (ORCPT ); Tue, 30 Jan 2018 17:39:20 -0500 Date: Tue, 30 Jan 2018 14:37:14 -0800 From: tip-bot for Dan Williams Message-ID: Cc: luto@kernel.org, torvalds@linux-foundation.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, hpa@zytor.com, dan.j.williams@intel.com, mingo@kernel.org Reply-To: dan.j.williams@intel.com, hpa@zytor.com, mingo@kernel.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, luto@kernel.org, torvalds@linux-foundation.org In-Reply-To: <151727417984.33451.1216731042505722161.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151727417984.33451.1216731042505722161.stgit@dwillia2-desk3.amr.corp.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/pti] x86/syscall: Sanitize syscall table de-references under speculation Git-Commit-ID: 2fbd7af5af8665d18bcefae3e9700be07e22b681 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: 2fbd7af5af8665d18bcefae3e9700be07e22b681 Gitweb: https://git.kernel.org/tip/2fbd7af5af8665d18bcefae3e9700be07e22b681 Author: Dan Williams AuthorDate: Mon, 29 Jan 2018 17:02:59 -0800 Committer: Thomas Gleixner CommitDate: Tue, 30 Jan 2018 21:54:31 +0100 x86/syscall: Sanitize syscall table de-references under speculation The syscall table base is a user controlled function pointer in kernel space. Use array_index_nospec() to prevent any out of bounds speculation. While retpoline prevents speculating into a userspace directed target it does not stop the pointer de-reference, the concern is leaking memory relative to the syscall table base, by observing instruction cache behavior. Reported-by: Linus Torvalds Signed-off-by: Dan Williams Signed-off-by: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: kernel-hardening@lists.openwall.com Cc: gregkh@linuxfoundation.org Cc: Andy Lutomirski Cc: alan@linux.intel.com Link: https://lkml.kernel.org/r/151727417984.33451.1216731042505722161.stgit@dwillia2-desk3.amr.corp.intel.com --- arch/x86/entry/common.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 9908134..21dbdf0 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -21,6 +21,7 @@ #include #include #include +#include #include #include #include @@ -282,7 +283,8 @@ __visible void do_syscall_64(struct pt_regs *regs) * regs->orig_ax, which changes the behavior of some syscalls. */ if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) { - regs->ax = sys_call_table[nr & __SYSCALL_MASK]( + nr = array_index_nospec(nr & __SYSCALL_MASK, NR_syscalls); + regs->ax = sys_call_table[nr]( regs->di, regs->si, regs->dx, regs->r10, regs->r8, regs->r9); } @@ -318,6 +320,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) } if (likely(nr < IA32_NR_syscalls)) { + nr = array_index_nospec(nr, IA32_NR_syscalls); /* * It's possible that a 32-bit syscall implementation * takes a 64-bit parameter but nonetheless assumes that