From 69e2387f3bfd408c7fb6c0d14b83d792f67ed638 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Fri, 8 Nov 2013 15:03:39 +0000 Subject: [PATCH] staging: comedi: kcomedilib: protect against device detachment The functions in "kcomedilib" need to prevent the comedi device being detached during their operation. This can be done by acquiring either the main mutex or the "attach lock" semaphore in the `struct comedi_device`. Use the attach lock when merely checking whether the device is attached. Use the mutex when processing a comedi instruction. Also, don't bother trying to manipulate the module use count of low-level comedi driver in `comedi_open()` and `comedi_close()`. If the device gets detached while it is "open", we wouldn't be able to decrement the module use count anyway. Signed-off-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- .../comedi/kcomedilib/kcomedilib_main.c | 57 ++++++++++++------- 1 file changed, 35 insertions(+), 22 deletions(-) diff --git a/drivers/staging/comedi/kcomedilib/kcomedilib_main.c b/drivers/staging/comedi/kcomedilib/kcomedilib_main.c index b3a06f2dbad6..7dc5a18e69d4 100644 --- a/drivers/staging/comedi/kcomedilib/kcomedilib_main.c +++ b/drivers/staging/comedi/kcomedilib/kcomedilib_main.c @@ -50,10 +50,12 @@ struct comedi_device *comedi_open(const char *filename) if (!dev) return NULL; - if (dev->attached && try_module_get(dev->driver->module)) + down_read(&dev->attach_lock); + if (dev->attached) retval = dev; else retval = NULL; + up_read(&dev->attach_lock); if (retval == NULL) comedi_dev_put(dev); @@ -62,13 +64,9 @@ struct comedi_device *comedi_open(const char *filename) } EXPORT_SYMBOL_GPL(comedi_open); -int comedi_close(struct comedi_device *d) +int comedi_close(struct comedi_device *dev) { - struct comedi_device *dev = (struct comedi_device *)d; - - module_put(dev->driver->module); comedi_dev_put(dev); - return 0; } EXPORT_SYMBOL_GPL(comedi_close); @@ -78,7 +76,14 @@ static int comedi_do_insn(struct comedi_device *dev, unsigned int *data) { struct comedi_subdevice *s; - int ret = 0; + int ret; + + mutex_lock(&dev->mutex); + + if (!dev->attached) { + ret = -EINVAL; + goto error; + } /* a subdevice instruction */ if (insn->subdev >= dev->n_subdevices) { @@ -125,6 +130,7 @@ static int comedi_do_insn(struct comedi_device *dev, s->busy = NULL; error: + mutex_unlock(&dev->mutex); return ret; } @@ -174,9 +180,6 @@ int comedi_dio_bitfield2(struct comedi_device *dev, unsigned int subdev, unsigned int shift; int ret; - if (subdev >= dev->n_subdevices) - return -EINVAL; - base_channel = CR_CHAN(base_channel); n_chan = comedi_get_n_channels(dev, subdev); if (base_channel >= n_chan) @@ -216,23 +219,33 @@ int comedi_find_subdevice_by_type(struct comedi_device *dev, int type, unsigned int subd) { struct comedi_subdevice *s; - - if (subd > dev->n_subdevices) - return -ENODEV; - - for (; subd < dev->n_subdevices; subd++) { - s = &dev->subdevices[subd]; - if (s->type == type) - return subd; - } - return -1; + int ret = -ENODEV; + + down_read(&dev->attach_lock); + if (dev->attached) + for (; subd < dev->n_subdevices; subd++) { + s = &dev->subdevices[subd]; + if (s->type == type) { + ret = subd; + break; + } + } + up_read(&dev->attach_lock); + return ret; } EXPORT_SYMBOL_GPL(comedi_find_subdevice_by_type); int comedi_get_n_channels(struct comedi_device *dev, unsigned int subdevice) { - struct comedi_subdevice *s = &dev->subdevices[subdevice]; + int n; + + down_read(&dev->attach_lock); + if (!dev->attached || subdevice >= dev->n_subdevices) + n = 0; + else + n = dev->subdevices[subdevice].n_chan; + up_read(&dev->attach_lock); - return s->n_chan; + return n; } EXPORT_SYMBOL_GPL(comedi_get_n_channels); -- 2.20.1