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    Subject[PATCH 2.6.32 09/38] [PATCH 09/38] xhci: fix off by one error in TRB DMA address boundary check
    Date
    2.6.32-longterm review patch.  If anyone has any objections, please let me know.

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

    commit 7895086afde2a05fa24a0e410d8e6b75ca7c8fdd upstream.

    We need to check that a TRB is part of the current segment
    before calculating its DMA address.

    Previously a ring segment didn't use a full memory page, and every
    new ring segment got a new memory page, so the off by one
    error in checking the upper bound was never seen.

    Now that we use a full memory page, 256 TRBs (4096 bytes), the off by one
    didn't catch the case when a TRB was the first element of the next segment.

    This is triggered if the virtual memory pages for a ring segment are
    next to each in increasing order where the ring buffer wraps around and
    causes errors like:

    [ 106.398223] xhci_hcd 0000:00:14.0: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 0 comp_code 1
    [ 106.398230] xhci_hcd 0000:00:14.0: Looking for event-dma fffd3000 trb-start fffd4fd0 trb-end fffd5000 seg-start fffd4000 seg-end fffd4ff0

    The trb-end address is one outside the end-seg address.

    Tested-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
    Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    (cherry picked from commit 6e3ae6256145b5597bee0296eb5fc384cd86aa3d)
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    drivers/usb/host/xhci-ring.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
    index 38fb682..fa22638 100644
    --- a/drivers/usb/host/xhci-ring.c
    +++ b/drivers/usb/host/xhci-ring.c
    @@ -80,7 +80,7 @@ dma_addr_t xhci_trb_virt_to_dma(struct xhci_segment *seg,
    return 0;
    /* offset in TRBs */
    segment_offset = trb - seg->trbs;
    - if (segment_offset > TRBS_PER_SEGMENT)
    + if (segment_offset >= TRBS_PER_SEGMENT)
    return 0;
    return seg->dma + (segment_offset * sizeof(*trb));
    }
    --
    1.7.12.2.21.g234cd45.dirty




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