| Message ID | 20181109231637.231582-1-venkateshs@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | uio/uio_pci_generic: Disable bus-mastering on release | expand |
On Fri, Nov 09, 2018 at 06:16:37PM -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@google.com> > Reviewed-by: Bjorn Helgaas <bhelgaas@google.com> > Reviewed-by: Catherine Sullivan <csully@google.com> > --- > drivers/uio/uio_pci_generic.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c > index 8773e373ffe5..832af15678ef 100644 > --- a/drivers/uio/uio_pci_generic.c > +++ b/drivers/uio/uio_pci_generic.c > @@ -39,6 +39,14 @@ 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); An empty line would add readability here. > + /* Stop the device from initiating further DMAs */ UIO is intended for non-DMA capable devices, since it doesn't enforce IOMMU protection. So this "further DMA" worries me as it might make people think it's ok. How about: /* 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 +86,7 @@ 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; > -- > 2.19.1.930.g4563a0d9d0-goog
diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c index 8773e373ffe5..832af15678ef 100644 --- a/drivers/uio/uio_pci_generic.c +++ b/drivers/uio/uio_pci_generic.c @@ -39,6 +39,14 @@ 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); + /* Stop the device from initiating further DMAs */ + 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 +86,7 @@ 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;