Hub driver will try to disable a USB3 device twice at logical disconnect, racing with xhci_free_dev() callback from the first port disable.

This can be triggered with "udisksctl power-off --block-device <disk>" or by writing "1" to the "remove" sysfs file for a USB3 device in 4.17-rc4.

USB3 devices don't have a similar disabled link state as USB2 devices, and use a U3 suspended link state instead. In this state the port is still enabled and connected.

hub_port_connect() first disconnects the device, then later it notices that device is still enabled (due to U3 states) it will try to disable the port again (set to U3).

The xhci_free_dev() called during device disable is async, so checking for existing xhci->devs[i] when setting link state to U3 the second time was successful, even if device was being freed.

The regression was caused by, and whole thing revealed by, Commit 44a182b9d177 ("xhci: Fix use-after-free in xhci_free_virt_device") which sets xhci->devs[i]->udev to NULL before xhci_virt_dev() returned. and causes a NULL pointer dereference the second time we try to set U3.

Fix this by checking xhci->devs[i]->udev exists before setting link state.

The original patch went to stable so this fix needs to be applied there as well.

Fixes: 44a182b9d177 ("xhci: Fix use-after-free in xhci_free_virt_device") Cc: stable@vger.kernel.org Reported-by: Jordan Glover Golden_Miller83@protonmail.ch Tested-by: Jordan Glover Golden_Miller83@protonmail.ch Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com --- drivers/usb/host/xhci-hub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c index 72ebbc9..32cd52c 100644 --- a/drivers/usb/host/xhci-hub.c +++ b/drivers/usb/host/xhci-hub.c @@ -354,7 +354,7 @@ int xhci_find_slot_id_by_port(struct usb_hcd *hcd, struct xhci_hcd *xhci,

slot_id = 0; for (i = 0; i < MAX_HC_SLOTS; i++) { - if (!xhci->devs[i]) + if (!xhci->devs[i] || !xhci->devs[i]->udev) continue; speed = xhci->devs[i]->udev->speed; if (((speed >= USB_SPEED_SUPER) == (hcd->speed >= HCD_USB3))