From: Venkatesh Srinivas <venkateshs@xxxxxxxxxx>
Userspace code using uio_pci_generic may enable bus-mastering by
directly manipulating a PCI device's command register. If a userspace
program enables bus-mastering but exits/crashes uncleanly, bus-
mastering will still be enabled and stale DMA addresses may be
programmed and live in the device.
Disable bus-mastering unconditionally on last close of a UIO PCI fd
to avoid this. If the device did not have bus-mastering enabled,
pci_clear_master() is a no-op.
Signed-off-by: Venkatesh Srinivas <venkateshs@xxxxxxxxxx>
Reviewed-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Catherine Sullivan <csully@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
drivers/uio/uio_pci_generic.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
index 8773e373ffe5..dde5cbb27178 100644
--- a/drivers/uio/uio_pci_generic.c
+++ b/drivers/uio/uio_pci_generic.c
@@ -39,6 +39,22 @@ to_uio_pci_generic_dev(struct uio_info *info)
return container_of(info, struct uio_pci_generic_dev, info);
}
+static int release(struct uio_info *info, struct inode *inode)
+{
+ struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
+
+ /*
+ * This driver is insecure when used with devices doing DMA, but some
+ * people (mis)use it with such devices.
+ * Let's at least make sure DMA isn't left enabled after the userspace
+ * driver closes the fd.
+ * Note that there's a non-zero chance doing this will wedge the device
+ * at least until reset.
+ */
+ pci_clear_master(gdev->pdev);
+ return 0;
+}
+
/* Interrupt handler. Read/modify/write the command register to disable
* the interrupt. */
static irqreturn_t irqhandler(int irq, struct uio_info *info)
@@ -78,6 +94,7 @@ static int probe(struct pci_dev *pdev,
gdev->info.name = "uio_pci_generic";
gdev->info.version = DRIVER_VERSION;
+ gdev->info.release = release;
gdev->pdev = pdev;
if (pdev->irq) {
gdev->info.irq = pdev->irq;
--
2.17.1
