From: Matthew Garrett <mjg59@srcf.ucam.org>
Date: Mon, 19 Aug 2019 17:17:47 -0700
Subject: PCI: Lock down BAR access when the kernel is locked down
Patch-mainline: v5.4-rc1
Git-commit: eb627e17727ebeede70697ae1798688b0d328b54
References: jsc#SLE-9870

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: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: linux-pci@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 drivers/pci/pci-sysfs.c      |   16 ++++++++++++++++
 drivers/pci/proc.c           |   14 ++++++++++++--
 drivers/pci/syscall.c        |    4 +++-
 include/linux/security.h     |    1 +
 security/lockdown/lockdown.c |    1 +
 5 files changed, 33 insertions(+), 3 deletions(-)

--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -906,6 +906,11 @@ static ssize_t pci_write_config(struct f
 	unsigned int size = count;
 	loff_t init_off = off;
 	u8 *data = (u8 *) buf;
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
 
 	if (off > dev->cfg_size)
 		return 0;
@@ -1167,6 +1172,11 @@ static int pci_mmap_resource(struct kobj
 	int bar = (unsigned long)attr->private;
 	enum pci_mmap_state mmap_type;
 	struct resource *res = &pdev->resource[bar];
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
 
 	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
 		return -EINVAL;
@@ -1243,6 +1253,12 @@ static ssize_t pci_write_resource_io(str
 				     struct bin_attribute *attr, char *buf,
 				     loff_t off, size_t count)
 {
+	int ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
+
 	return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -13,6 +13,7 @@
 #include <linux/seq_file.h>
 #include <linux/capability.h>
 #include <linux/uaccess.h>
+#include <linux/security.h>
 #include <asm/byteorder.h>
 #include "pci.h"
 
@@ -115,7 +116,11 @@ static ssize_t proc_bus_pci_write(struct
 	struct pci_dev *dev = PDE_DATA(ino);
 	int pos = *ppos;
 	int size = dev->cfg_size;
-	int cnt;
+	int cnt, ret;
+
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
 
 	if (pos >= size)
 		return 0;
@@ -196,6 +201,10 @@ static long proc_bus_pci_ioctl(struct fi
 #endif /* HAVE_PCI_MMAP */
 	int ret = 0;
 
+	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
+	if (ret)
+		return ret;
+
 	switch (cmd) {
 	case PCIIOC_CONTROLLER:
 		ret = pci_domain_nr(dev->bus);
@@ -238,7 +247,8 @@ 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) ||
+	    security_locked_down(LOCKDOWN_PCI_ACCESS))
 		return -EPERM;
 
 	if (fpriv->mmap_state == pci_mmap_io) {
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -7,6 +7,7 @@
 
 #include <linux/errno.h>
 #include <linux/pci.h>
+#include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/uaccess.h>
 #include "pci.h"
@@ -90,7 +91,8 @@ SYSCALL_DEFINE5(pciconfig_write, unsigne
 	u32 dword;
 	int err = 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) ||
+	    security_locked_down(LOCKDOWN_PCI_ACCESS))
 		return -EPERM;
 
 	dev = pci_get_domain_bus_and_slot(0, bus, dfn);
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -107,6 +107,7 @@ enum lockdown_reason {
 	LOCKDOWN_DEV_MEM,
 	LOCKDOWN_KEXEC,
 	LOCKDOWN_HIBERNATION,
+	LOCKDOWN_PCI_ACCESS,
 	LOCKDOWN_INTEGRITY_MAX,
 	LOCKDOWN_CONFIDENTIALITY_MAX,
 };
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c
@@ -22,6 +22,7 @@ static char *lockdown_reasons[LOCKDOWN_C
 	[LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
 	[LOCKDOWN_KEXEC] = "kexec of unsigned images",
 	[LOCKDOWN_HIBERNATION] = "hibernation",
+	[LOCKDOWN_PCI_ACCESS] = "direct PCI access",
 	[LOCKDOWN_INTEGRITY_MAX] = "integrity",
 	[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
 };