[PATCH 3.16 059/134] PCI: Only allow WC mmap on prefetchable resources

Ben Hutchings
2017-08-18T13:15:46Z

From: David Woodhouse <dwmw@amazon.co.uk>

commit cef4d02305a06be581bb7f4353446717a1b319ec upstream.

The /proc/bus/pci mmap interface allows the user to specify whether they
want WC or not. Don't let them do so on non-prefetchable BARs.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/pci/proc.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -231,7 +231,7 @@ static int proc_bus_pci_mmap(struct file
{
struct pci_dev *dev = PDE_DATA(file_inode(file));
struct pci_filp_private *fpriv = file->private_data;
- int i, ret, write_combine, res_bit;
+ int i, ret, write_combine = 0, res_bit;

if (!capable(CAP_SYS_RAWIO))
return -EPERM;
@@ -251,10 +251,13 @@ static int proc_bus_pci_mmap(struct file
if (i >= PCI_ROM_RESOURCE)
return -ENODEV;

- if (fpriv->mmap_state == pci_mmap_mem)
- write_combine = fpriv->write_combine;
- else
- write_combine = 0;
+ if (fpriv->mmap_state == pci_mmap_mem &&
+ fpriv->write_combine) {
+ if (dev->resource[i].flags & IORESOURCE_PREFETCH)
+ write_combine = 1;
+ else
+ return -EINVAL;
+ }
ret = pci_mmap_page_range(dev, vma,
fpriv->mmap_state, write_combine);
if (ret < 0)