staging: comedi: amplc_pc236: fix possible NULL deref during detach
`pc236_detach()` is called by the comedi core to clean up if either `pc236_attach()` or `pc236_attach_pci()` returns an error. It sets `thisboard` to the return value of `comedi_board(dev)` and assumes it is non-null. This is a valid assumption if `pc236_attach()` fails, but not if `pc236_attach_pci()` fails, leading to a possible NULL pointer dereference. Check `thisboard` at the top of `pc236_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. Cc: <stable@vger.kernel.org> # 3.6.x Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -574,6 +574,8 @@ static void pc236_detach(struct comedi_device *dev)
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{
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const struct pc236_board *thisboard = comedi_board(dev);
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if (!thisboard)
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return;
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if (dev->iobase)
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pc236_intr_disable(dev);
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if (dev->irq)
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