From 6f756b32a45b022428e33ce20181e874c73ca82e Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Thu, 8 Mar 2012 10:10:38 -0500
Subject: [PATCH] PCI: Lock down BAR access when module security is enabled

Any hardware that can potentially generate DMA has to be locked down from
userspace in order to avoid it being possible for an attacker to modify
kernel code, allowing them to circumvent disabled module loading or module
signing. Default to paranoid - in future we can potentially relax this for
sufficiently IOMMU-isolated devices.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
---
 drivers/pci/pci-sysfs.c | 10 ++++++++++
 drivers/pci/proc.c      |  8 +++++++-
 drivers/pci/syscall.c   |  3 ++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index bcd10c7..a950301 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -30,6 +30,7 @@
 #include <linux/vgaarb.h>
 #include <linux/pm_runtime.h>
 #include <linux/of.h>
+#include <linux/module.h>
 #include "pci.h"
 
 static int sysfs_initialized;	/* = 0 */
@@ -716,6 +717,9 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
 	loff_t init_off = off;
 	u8 *data = (u8 *) buf;
 
+	if (secure_modules())
+		return -EPERM;
+
 	if (off > dev->cfg_size)
 		return 0;
 	if (off + count > dev->cfg_size) {
@@ -1007,6 +1011,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
 	resource_size_t start, end;
 	int i;
 
+	if (secure_modules())
+		return -EPERM;
+
 	for (i = 0; i < PCI_ROM_RESOURCE; i++)
 		if (res == &pdev->resource[i])
 			break;
@@ -1106,6 +1113,9 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
 				     struct bin_attribute *attr, char *buf,
 				     loff_t off, size_t count)
 {
+	if (secure_modules())
+		return -EPERM;
+
 	return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 2408abe..59f321c 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -116,6 +116,9 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
 	int size = dev->cfg_size;
 	int cnt;
 
+	if (secure_modules())
+		return -EPERM;
+
 	if (pos >= size)
 		return 0;
 	if (nbytes >= size)
@@ -195,6 +198,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
 	int ret = 0;
 
+	if (secure_modules())
+		return -EPERM;
+
 	switch (cmd) {
 	case PCIIOC_CONTROLLER:
 		ret = pci_domain_nr(dev->bus);
@@ -233,7 +239,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
 	struct pci_filp_private *fpriv = file->private_data;
 	int i, ret, write_combine;
 
-	if (!capable(CAP_SYS_RAWIO))
+	if (!capable(CAP_SYS_RAWIO) || secure_modules())
 		return -EPERM;
 
 	/* Make sure the caller is mapping a real resource for this device */
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index b91c4da..98f5637 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -10,6 +10,7 @@
 #include <linux/errno.h>
 #include <linux/pci.h>
 #include <linux/syscalls.h>
+#include <linux/module.h>
 #include <asm/uaccess.h>
 #include "pci.h"
 
@@ -92,7 +93,7 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
 	u32 dword;
 	int err = 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) || secure_modules())
 		return -EPERM;
 
 	dev = pci_get_bus_and_slot(bus, dfn);
-- 
2.9.2