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authorVenkatesh Srinivas <venkateshs@google.com>2019-01-23 11:27:51 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-01-31 16:22:51 +0100
commit865a11f987ab5f03089b2728420b61a2a1f7051a (patch)
tree297392fb063a48e7b8faa6db2759453703dc6030 /drivers/uio
parente5bae74338b37fb88d33d7c18acb694670c24b09 (diff)
downloadlinux-865a11f987ab5f03089b2728420b61a2a1f7051a.tar.bz2
uio/uio_pci_generic: Disable bus-mastering on release
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>
Diffstat (limited to 'drivers/uio')
-rw-r--r--drivers/uio/uio_pci_generic.c17
1 files changed, 17 insertions, 0 deletions
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;