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    Subject[PATCH 4.4 46/56] xhci: Fix use-after-free in xhci_free_virt_device
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Mathias Nyman <mathias.nyman@linux.intel.com>

    commit 44a182b9d17765514fa2b1cc911e4e65134eef93 upstream.

    KASAN found a use-after-free in xhci_free_virt_device+0x33b/0x38e
    where xhci_free_virt_device() sets slot id to 0 if udev exists:
    if (dev->udev && dev->udev->slot_id)
    dev->udev->slot_id = 0;

    dev->udev will be true even if udev is freed because dev->udev is
    not set to NULL.

    set dev->udev pointer to NULL in xhci_free_dev()

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

    Fixes: a400efe455f7 ("xhci: zero usb device slot_id member when disabling and freeing a xhci slot")
    Cc: <stable@vger.kernel.org>
    Reported-by: Guenter Roeck <linux@roeck-us.net>
    Reviewed-by: Guenter Roeck <linux@roeck-us.net>
    Tested-by: Guenter Roeck <linux@roeck-us.net>
    Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
    Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/usb/host/xhci.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/drivers/usb/host/xhci.c
    +++ b/drivers/usb/host/xhci.c
    @@ -3675,6 +3675,9 @@ void xhci_free_dev(struct usb_hcd *hcd,
    }

    spin_lock_irqsave(&xhci->lock, flags);
    +
    + virt_dev->udev = NULL;
    +
    /* Don't disable the slot if the host controller is dead. */
    state = readl(&xhci->op_regs->status);
    if (state == 0xffffffff || (xhci->xhc_state & XHCI_STATE_DYING) ||

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