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    Subject[PATCH 5.2 167/215] xhci: Fix crash if scatter gather is used with Immediate Data Transfer (IDT).
    Date
    From: Mathias Nyman <mathias.nyman@linux.intel.com>

    commit d39b5bad8658d6d94cb2d98a44a7e159db4f5030 upstream.

    A second regression was found in the immediate data transfer (IDT)
    support which was added to 5.2 kernel

    IDT is used to transfer small amounts of data (up to 8 bytes) in the
    field normally used for data dma address, thus avoiding dma mapping.

    If the data was not already dma mapped, then IDT support assumed data was
    in urb->transfer_buffer, and did not take into accound that even
    small amounts of data (8 bytes) can be in a scatterlist instead.

    This caused a NULL pointer dereference when sg_dma_len() was used
    with non-dma mapped data.

    Solve this by not using IDT if scatter gather buffer list is used.

    Fixes: 33e39350ebd2 ("usb: xhci: add Immediate Data Transfer support")
    Cc: <stable@vger.kernel.org> # v5.2
    Reported-by: Maik Stohn <maik.stohn@seal-one.com>
    Tested-by: Maik Stohn <maik.stohn@seal-one.com>
    CC: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
    Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
    Link: https://lore.kernel.org/r/1564044861-1445-1-git-send-email-mathias.nyman@linux.intel.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/usb/host/xhci.h | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/drivers/usb/host/xhci.h
    +++ b/drivers/usb/host/xhci.h
    @@ -2170,7 +2170,8 @@ static inline bool xhci_urb_suitable_for
    if (!usb_endpoint_xfer_isoc(&urb->ep->desc) && usb_urb_dir_out(urb) &&
    usb_endpoint_maxp(&urb->ep->desc) >= TRB_IDT_MAX_SIZE &&
    urb->transfer_buffer_length <= TRB_IDT_MAX_SIZE &&
    - !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP))
    + !(urb->transfer_flags & URB_NO_TRANSFER_DMA_MAP) &&
    + !urb->num_sgs)
    return true;

    return false;

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