Bah, I made a mistake in my first patch, try this one instead. Sarah Sharp 8<------------------------------------------------------------------>8 When the host controller fails to respond to an Enable Slot command, and the host fails to respond to the register write to abort the command ring, the xHCI driver will assume the host is dead, and call usb_hc_died(). The USB device's slot_id is still set to zero, and the pointer stored at xhci->devs[0] will always be NULL. The call to xhci_check_args in xhci_free_dev should have caught the NULL virt_dev pointer. However, xhci_free_dev is designed to free the xhci_virt_device structures, even if the host is dead, so that we don't leak kernel memory. xhci_free_dev checks the return value from the generic xhci_check_args function. If the return value is -ENODEV, it carries on trying to free the virtual device. The issue is that xhci_check_args looks at the host controller state before it looks at the xhci_virt_device pointer. It will return -ENIVAL because the host is dead, and xhci_free_dev will ignore the return value, and happily dereference the NULL xhci_virt_device pointer. The fix is to make sure that xhci_check_args checks the xhci_virt_device pointer before it checks the host state. See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1203453 for further details. This patch doesn't solve the underlying issue, but will ensure we don't see any more NULL pointer dereferences because of the issue. This patch should be backported to kernels as old as 3.1, that contain the commit 7bd89b4017f46a9b92853940fd9771319acb578a "xhci: Don't submit commands or URBs to halted hosts." Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> Reported-by: Vincent Thiele <vincentthiele@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> --- drivers/usb/host/xhci.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index 2c49f00..98aac74 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -1181,9 +1181,6 @@ static int xhci_check_args(struct usb_hcd *hcd, struct usb_device *udev, } xhci = hcd_to_xhci(hcd); - if (xhci->xhc_state & XHCI_STATE_HALTED) - return -ENODEV; - if (check_virt_dev) { if (!udev->slot_id || !xhci->devs[udev->slot_id]) { printk(KERN_DEBUG "xHCI %s called with unaddressed " @@ -1199,6 +1196,9 @@ static int xhci_check_args(struct usb_hcd *hcd, struct usb_device *udev, } } + if (xhci->xhc_state & XHCI_STATE_HALTED) + return -ENODEV; + return 1; } -- 1.7.9 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
