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

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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>
This commit is contained in:
Matthew Garrett
2019-08-19 17:17:47 -07:00
committed by James Morris
parent 38bd94b8a1
commit eb627e1772
5 changed files with 33 additions and 3 deletions
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14
drivers/pci/proc.c
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@@ -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) {