PCI: Only allow WC mmap on prefetchable resources

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>
Cc: stable@vger.kernel.org

1 files changed, 8 insertions, 5 deletions

diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 62a0c3e788d3..dc8912e2d4a1 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -231,7 +231,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
 {
         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 *file, struct vm_area_struct *vma)
         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)