Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754077AbaBZUOM (ORCPT ); Wed, 26 Feb 2014 15:14:12 -0500 Received: from cavan.codon.org.uk ([93.93.128.6]:44121 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753729AbaBZULl (ORCPT ); Wed, 26 Feb 2014 15:11:41 -0500 From: Matthew Garrett To: linux-kernel@vger.kernel.org Cc: keescook@chromium.org, gregkh@linuxfoundation.org, hpa@zytor.com, linux-efi@vger.kernel.org, jmorris@namei.org, linux-security-module@vger.kernel.org, Matthew Garrett Subject: [PATCH 04/12] x86: Lock down IO port access when trusted_kernel is true Date: Wed, 26 Feb 2014 15:11:05 -0500 Message-Id: <1393445473-15068-5-git-send-email-matthew.garrett@nebula.com> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1393445473-15068-1-git-send-email-matthew.garrett@nebula.com> References: <1393445473-15068-1-git-send-email-matthew.garrett@nebula.com> X-SA-Do-Not-Run: Yes X-SA-Exim-Connect-IP: 209.6.207.143 X-SA-Exim-Mail-From: matthew.garrett@nebula.com X-SA-Exim-Scanned: No (on cavan.codon.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org IO port access would permit users to gain access to PCI configuration registers, which in turn (on a lot of hardware) give access to MMIO register space. This would potentially permit root to trigger arbitrary DMA, so lock it down when trusted_kernel is true Signed-off-by: Matthew Garrett --- arch/x86/kernel/ioport.c | 5 +++-- drivers/char/mem.c | 7 +++++++ 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c index 4ddaf66..3121541 100644 --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -15,6 +15,7 @@ #include #include #include +#include #include /* @@ -28,7 +29,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) return -EINVAL; - if (turn_on && !capable(CAP_SYS_RAWIO)) + if (turn_on && (!capable(CAP_SYS_RAWIO) || (get_trusted_kernel()))) return -EPERM; /* @@ -103,7 +104,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level) return -EINVAL; /* Trying to gain more privileges? */ if (level > old) { - if (!capable(CAP_SYS_RAWIO)) + if (!capable(CAP_SYS_RAWIO) || (get_trusted_kernel())) return -EPERM; } regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12); diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 92c5937..15331a8 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -27,6 +27,7 @@ #include #include #include +#include #include @@ -544,6 +545,9 @@ static ssize_t read_port(struct file *file, char __user *buf, unsigned long i = *ppos; char __user *tmp = buf; + if (get_trusted_kernel()) + return -EPERM; + if (!access_ok(VERIFY_WRITE, buf, count)) return -EFAULT; while (count-- > 0 && i < 65536) { @@ -562,6 +566,9 @@ static ssize_t write_port(struct file *file, const char __user *buf, unsigned long i = *ppos; const char __user *tmp = buf; + if (get_trusted_kernel()) + return -EPERM; + if (!access_ok(VERIFY_READ, buf, count)) return -EFAULT; while (count-- > 0 && i < 65536) { -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/