From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753962AbcARDZE (ORCPT ); Sun, 17 Jan 2016 22:25:04 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:59410 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753142AbcARDWF (ORCPT ); Sun, 17 Jan 2016 22:22:05 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David Vrabel" , "Jan Beulich" , "Konrad Rzeszutek Wilk" Date: Mon, 18 Jan 2016 03:18:35 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 24/70] xen/pciback: Save xen_pci_op commands before processing it In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.247 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.76-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Konrad Rzeszutek Wilk commit 8135cf8b092723dbfcc611fe6fdcb3a36c9951c5 upstream. Double fetch vulnerabilities that happen when a variable is fetched twice from shared memory but a security check is only performed the first time. The xen_pcibk_do_op function performs a switch statements on the op->cmd value which is stored in shared memory. Interestingly this can result in a double fetch vulnerability depending on the performed compiler optimization. This patch fixes it by saving the xen_pci_op command before processing it. We also use 'barrier' to make sure that the compiler does not perform any optimization. This is part of XSA155. Reviewed-by: Konrad Rzeszutek Wilk Signed-off-by: Jan Beulich Signed-off-by: David Vrabel Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Ben Hutchings --- drivers/xen/xen-pciback/pciback.h | 1 + drivers/xen/xen-pciback/pciback_ops.c | 15 ++++++++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) --- a/drivers/xen/xen-pciback/pciback.h +++ b/drivers/xen/xen-pciback/pciback.h @@ -37,6 +37,7 @@ struct xen_pcibk_device { struct xen_pci_sharedinfo *sh_info; unsigned long flags; struct work_struct op_work; + struct xen_pci_op op; }; struct xen_pcibk_dev_data { --- a/drivers/xen/xen-pciback/pciback_ops.c +++ b/drivers/xen/xen-pciback/pciback_ops.c @@ -296,9 +296,11 @@ void xen_pcibk_do_op(struct work_struct container_of(data, struct xen_pcibk_device, op_work); struct pci_dev *dev; struct xen_pcibk_dev_data *dev_data = NULL; - struct xen_pci_op *op = &pdev->sh_info->op; + struct xen_pci_op *op = &pdev->op; int test_intx = 0; + *op = pdev->sh_info->op; + barrier(); dev = xen_pcibk_get_pci_dev(pdev, op->domain, op->bus, op->devfn); if (dev == NULL) @@ -340,6 +342,17 @@ void xen_pcibk_do_op(struct work_struct if ((dev_data->enable_intx != test_intx)) xen_pcibk_control_isr(dev, 0 /* no reset */); } + pdev->sh_info->op.err = op->err; + pdev->sh_info->op.value = op->value; +#ifdef CONFIG_PCI_MSI + if (op->cmd == XEN_PCI_OP_enable_msix && op->err == 0) { + unsigned int i; + + for (i = 0; i < op->value; i++) + pdev->sh_info->op.msix_entries[i].vector = + op->msix_entries[i].vector; + } +#endif /* Tell the driver domain that we're done. */ wmb(); clear_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);