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uio/uio_pci_generic: Disable bus-mastering on release

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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@google.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Catherine Sullivan <csully@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Venkatesh Srinivas 2019-01-23 11:27:51 +00:00 committed by Greg Kroah-Hartman
parent e5bae74338
commit 865a11f987
1 changed files with 17 additions and 0 deletions
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17
drivers/uio/uio_pci_generic.c
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@ -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;