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

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Message-ID: <lsq.1503062000.48689409@decadent.org.uk>
Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David Woodhouse" <dwmw@...zon.co.uk>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>
Subject: [PATCH 3.16 059/134] PCI: Only allow WC mmap on prefetchable
 resources

3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: David Woodhouse <dwmw@...zon.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@...zon.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Signed-off-by: Ben Hutchings <ben@...adent.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)