From 865a11f987ab5f03089b2728420b61a2a1f7051a Mon Sep 17 00:00:00 2001 From: Venkatesh Srinivas Date: Wed, 23 Jan 2019 11:27:51 +0000 Subject: [PATCH] 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 Reviewed-by: Bjorn Helgaas Reviewed-by: Catherine Sullivan Acked-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman --- 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;