From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Wed, 8 Nov 2017 15:11:33 +0000
Subject: [11/29] PCI: Lock down BAR access when the kernel is locked down
Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=d107d11fd7ac982a34b1233722cb3e72f9fe5a20

Any hardware that can potentially generate DMA has to be locked down 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>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-pci@vger.kernel.org
---
 drivers/pci/pci-sysfs.c | 9 +++++++++
 drivers/pci/proc.c      | 9 ++++++++-
 drivers/pci/syscall.c   | 3 ++-
 3 files changed, 19 insertions(+), 2 deletions(-)

Index: linux/drivers/pci/pci-sysfs.c
===================================================================
--- linux.orig/drivers/pci/pci-sysfs.c
+++ linux/drivers/pci/pci-sysfs.c
@@ -905,6 +905,9 @@ static ssize_t pci_write_config(struct f
 	loff_t init_off = off;
 	u8 *data = (u8 *) buf;
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	if (off > dev->cfg_size)
 		return 0;
 	if (off + count > dev->cfg_size) {
@@ -1167,6 +1170,9 @@ static int pci_mmap_resource(struct kobj
 	enum pci_mmap_state mmap_type;
 	struct resource *res = &pdev->resource[bar];
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
 		return -EINVAL;
 
@@ -1242,6 +1248,9 @@ static ssize_t pci_write_resource_io(str
 				     struct bin_attribute *attr, char *buf,
 				     loff_t off, size_t count)
 {
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 
Index: linux/drivers/pci/proc.c
===================================================================
--- linux.orig/drivers/pci/proc.c
+++ linux/drivers/pci/proc.c
@@ -117,6 +117,9 @@ static ssize_t proc_bus_pci_write(struct
 	int size = dev->cfg_size;
 	int cnt;
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	if (pos >= size)
 		return 0;
 	if (nbytes >= size)
@@ -196,6 +199,9 @@ static long proc_bus_pci_ioctl(struct fi
 #endif /* HAVE_PCI_MMAP */
 	int ret = 0;
 
+	if (kernel_is_locked_down("Direct PCI access"))
+		return -EPERM;
+
 	switch (cmd) {
 	case PCIIOC_CONTROLLER:
 		ret = pci_domain_nr(dev->bus);
@@ -237,7 +243,8 @@ static int proc_bus_pci_mmap(struct file
 	struct pci_filp_private *fpriv = file->private_data;
 	int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
 
-	if (!capable(CAP_SYS_RAWIO))
+	if (!capable(CAP_SYS_RAWIO) ||
+	    kernel_is_locked_down("Direct PCI access"))
 		return -EPERM;
 
 	if (fpriv->mmap_state == pci_mmap_io) {
Index: linux/drivers/pci/syscall.c
===================================================================
--- linux.orig/drivers/pci/syscall.c
+++ linux/drivers/pci/syscall.c
@@ -90,7 +90,8 @@ SYSCALL_DEFINE5(pciconfig_write, unsigne
 	u32 dword;
 	int err = 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) ||
+	    kernel_is_locked_down("Direct PCI access"))
 		return -EPERM;
 
 	dev = pci_get_domain_bus_and_slot(0, bus, dfn);
