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staging/comedi: keep reference to class device after destroyed
When a dynamically allocated `struct comedi_device` gets automatically unconfigured by a call to `comedi_auto_unconfig()` from a lower-level driver's bus removal function (e.g. when a USB device is disconnected), the class device in `dev->class_dev` (where `dev` points to the `struct comedi_device`) is destroyed by a call to `device_destroy()` that matches a previous call to `device_create()`. However, if the `struct comedi_device` is still associated with an open file object, the now invalid `dev->class_dev` pointer may still be passed to `dev_printk()` (via `dev_dbg()` etc.), producing bogus output or worse. To fix this, call `get_device()` on the class device if `device_create()` was successful. Add a matching call to `put_device()` in `comedi_dev_kref_release()` when the `struct comedi_device` is freed. The calls to `dev_dbg()` etc. after the call to `device_destroy()` will still produce valid output, although the device will have been unregistered in sysfs. Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 2 additions and 1 deletions
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@ -91,6 +91,7 @@ static void comedi_dev_kref_release(struct kref *kref)
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container_of(kref, struct comedi_device, refcount);
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mutex_destroy(&dev->mutex);
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put_device(dev->class_dev);
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kfree(dev);
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}
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@ -2514,7 +2515,7 @@ struct comedi_device *comedi_alloc_board_minor(struct device *hardware_device)
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csdev = device_create(comedi_class, hardware_device,
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MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i", i);
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if (!IS_ERR(csdev))
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dev->class_dev = csdev;
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dev->class_dev = get_device(csdev);
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/* Note: dev->mutex needs to be unlocked by the caller. */
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return dev;
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