On Tue, Nov 13, 2018 at 08:08:58PM -0500, Venkatesh Srinivas wrote:
> 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>
Okay then.
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;
> --
> 2.19.1.1215.g8438c0b245-goog
