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    Subject[ 152/262] EHCI: Update qTD next pointer in QH overlay region during unlink
    Date
    From: Greg KH <gregkh@linuxfoundation.org>

    3.5-stable review patch. If anyone has any objections, please let me know.

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

    From: Pavankumar Kondeti <pkondeti@codeaurora.org>

    commit 3d037774b42ed677f699b1dce7d548d55f4e4c2b upstream.

    There is a possibility of QH overlay region having reference to a stale
    qTD pointer during unlink.

    Consider an endpoint having two pending qTD before unlink process begins.
    The endpoint's QH queue looks like this.

    qTD1 --> qTD2 --> Dummy

    To unlink qTD2, QH is removed from asynchronous list and Asynchronous
    Advance Doorbell is programmed. The qTD1's next qTD pointer is set to
    qTD2'2 next qTD pointer and qTD2 is retired upon controller's doorbell
    interrupt. If QH's current qTD pointer points to qTD1, transfer overlay
    region still have reference to qTD2. But qtD2 is just unlinked and freed.
    This may cause EHCI system error. Fix this by updating qTD next pointer
    in QH overlay region with the qTD next pointer of the current qTD.

    Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
    Acked-by: Alan Stern <stern@rowland.harvard.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/usb/host/ehci-q.c | 12 ++++++++++--
    1 file changed, 10 insertions(+), 2 deletions(-)

    --- a/drivers/usb/host/ehci-q.c
    +++ b/drivers/usb/host/ehci-q.c
    @@ -128,9 +128,17 @@ qh_refresh (struct ehci_hcd *ehci, struc
    else {
    qtd = list_entry (qh->qtd_list.next,
    struct ehci_qtd, qtd_list);
    - /* first qtd may already be partially processed */
    - if (cpu_to_hc32(ehci, qtd->qtd_dma) == qh->hw->hw_current)
    + /*
    + * first qtd may already be partially processed.
    + * If we come here during unlink, the QH overlay region
    + * might have reference to the just unlinked qtd. The
    + * qtd is updated in qh_completions(). Update the QH
    + * overlay here.
    + */
    + if (cpu_to_hc32(ehci, qtd->qtd_dma) == qh->hw->hw_current) {
    + qh->hw->hw_qtd_next = qtd->hw_next;
    qtd = NULL;
    + }
    }

    if (qtd)



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