On Fri, Mar 25, 2011 at 06:44:18PM +1100, Matt Evans wrote:
> During a "plug-unplug" stress test on an NEC xHCI card, a null pointer
> dereference was observed. xhci_address_device() dereferenced a null
> virt_dev (possibly an erroneous udev->slot_id?); this patch adds a WARN_ON &
> message to aid debug if it can be recreated.
Hmm, that's interesting. I haven't seen any null pointer dereferences
during my tests, but perhaps I'm not being ADDH enough about randomly
unplugging devices. :) Let me know if you trigger this again.
Sarah Sharp
> Signed-off-by: Matt Evans <matt@xxxxxxxxxx>
> ---
> drivers/usb/host/xhci.c | 11 +++++++++++
> 1 files changed, 11 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 88e6298..7d43456 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -2542,6 +2542,17 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
>
> virt_dev = xhci->devs[udev->slot_id];
>
> + if (WARN_ON(!virt_dev)) {
> + /*
> + * In plug/unplug torture test with an NEC controller,
> + * a zero-dereference was observed once due to virt_dev = 0.
> + * Print useful debug rather than crash if it is observed again!
> + */
> + xhci_warn(xhci, "Virt dev invalid for slot_id 0x%x!\n",
> + udev->slot_id);
> + return -EINVAL;
> + }
> +
> slot_ctx = xhci_get_slot_ctx(xhci, virt_dev->in_ctx);
> /*
> * If this is the first Set Address since device plug-in or
> --
> 1.7.0.4
>
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