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    Subject[ 030/101] staging: comedi: ni_labpc: fix possible NULL deref during detach
    Date
    3.6-stable review patch.  If anyone has any objections, please let me know.

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

    From: Ian Abbott <abbotti@mev.co.uk>

    commit 922b67c1ac53014d80649a961a2fde700cd065d8 upstream.

    `labpc_common_detach()` is called by the comedi core to clean up if
    either `labpc_attach()` (including the one in the "ni_labpc_cs" module)
    or `labpc_attach_pci()` returns an error. It assumes the `thisboard`
    macro (expanding to `((struct labpc_board_struct *)dev->board_ptr)`) is
    non-null. This is a valid assumption if `labpc_attach()` fails, but not
    if `labpc_attach_pci()` fails, leading to a possible NULL pointer
    dereference.

    Check `thisboard` at the top of `labpc_common_detach()` and return early
    if it is `NULL`. This is okay because the only other thing that could
    have been allocated is `dev->private` and that is freed by the comedi
    core, not by this function.

    Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/staging/comedi/drivers/ni_labpc.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/drivers/staging/comedi/drivers/ni_labpc.c
    +++ b/drivers/staging/comedi/drivers/ni_labpc.c
    @@ -809,6 +809,8 @@ static int labpc_find_device(struct come

    void labpc_common_detach(struct comedi_device *dev)
    {
    + if (!thisboard)
    + return;
    if (dev->subdevices)
    subdev_8255_cleanup(dev, dev->subdevices + 2);
    #ifdef CONFIG_ISA_DMA_API



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