Éric Piel reported a kernel oops in the "comedi_test" module. It was a NULL pointer dereference within `waveform_ai_interrupt()` (actually a timer function) that sometimes occurred when a running asynchronous command is cancelled (either by the `COMEDI_CANCEL` ioctl or by closing the device file). This seems to be a race between the caller of `waveform_ai_cancel()` which on return from that function goes and tears down the running command, and the timer function which uses the command. In particular, `async->cmd.chanlist` gets freed (and the pointer set to NULL) by `do_become_nonbusy()` in "comedi_fops.c" but a previously scheduled `waveform_ai_interrupt()` timer function will dereference that pointer regardless, leading to the oops. Fix it by replacing the `del_timer()` call in `waveform_ai_cancel()` with `del_timer_sync()`. Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx> Reported-by: Éric Piel <piel@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/staging/comedi/drivers/comedi_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c index fb3d093..01de996 100644 --- a/drivers/staging/comedi/drivers/comedi_test.c +++ b/drivers/staging/comedi/drivers/comedi_test.c @@ -345,7 +345,7 @@ static int waveform_ai_cancel(struct comedi_device *dev, struct waveform_private *devpriv = dev->private; devpriv->timer_running = 0; - del_timer(&devpriv->timer); + del_timer_sync(&devpriv->timer); return 0; } -- 1.8.0 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
