Commit eb627e17 authored by Matthew Garrett's avatar Matthew Garrett Committed by James Morris
Browse files

PCI: Lock down BAR access when the kernel is locked down 



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: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarMatthew Garrett <mjg59@google.com>
Acked-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
cc: linux-pci@vger.kernel.org
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent 38bd94b8

drivers/pci/pci-sysfs.c

+16 −0
Original line number Diff line number Diff line
@@ -903,6 +903,11 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj, 
	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;
@@ -1164,6 +1169,11 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr, 
	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;
@@ -1240,6 +1250,12 @@ 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)

{

	int ret;



	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);

	if (ret)

		return ret;



	return pci_resource_io(filp, kobj, attr, buf, off, count, true);

}

drivers/pci/proc.c

+12 −2
Original line number Diff line number Diff line
@@ -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 file *file, const char __user *buf, 
	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 file *file, unsigned int cmd, 
#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 *file, struct vm_area_struct *vma) 
	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) {

drivers/pci/syscall.c

+3 −1
Original line number Diff line number Diff line
@@ -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, unsigned long, bus, unsigned long, dfn, 
	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);

include/linux/security.h

+1 −0
Original line number Diff line number Diff line
@@ -107,6 +107,7 @@ enum lockdown_reason { 
	LOCKDOWN_DEV_MEM,

	LOCKDOWN_KEXEC,

	LOCKDOWN_HIBERNATION,

	LOCKDOWN_PCI_ACCESS,

	LOCKDOWN_INTEGRITY_MAX,

	LOCKDOWN_CONFIDENTIALITY_MAX,

};

security/lockdown/lockdown.c

+1 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { 
	[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",

};

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