staging: comedi: usbdux: prevent "empty acquisition" async commands

This driver currently allows a cmd->stop_src == TRIG_COUNT with a cmd->stop_arg
of 0 for both the analog input and output async commands. The (*do_cmd) for
both subdevices sets up and starts the command without handling the "empty
acquisition". This results in the interrupt functions trying to transfer 0 data
samples.

Validate that the cmd->stop_arg is >= 1 in the (*do_cmdtest) to prevent the
"empty acquisition".

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/usbdux.c b/drivers/staging/comedi/drivers/usbdux.c
index 8eb2742e6fef6a4ca373e42c9ee6a04fc3f7729d..5adbfedf780fc51845d442d7ab3165fb8769c668 100644 (file)
--- a/drivers/staging/comedi/drivers/usbdux.c
+++ b/drivers/staging/comedi/drivers/usbdux.c
@@ -623,12 +623,10 @@ static int usbdux_ai_cmdtest(struct comedi_device *dev,
 
        err |= cfc_check_trigger_arg_is(&cmd->scan_end_arg, cmd->chanlist_len);
 
-       if (cmd->stop_src == TRIG_COUNT) {
-               /* any count is allowed */
-       } else {
-               /* TRIG_NONE */
+       if (cmd->stop_src == TRIG_COUNT)
+               err |= cfc_check_trigger_arg_min(&cmd->stop_arg, 1);
+       else    /* TRIG_NONE */
                err |= cfc_check_trigger_arg_is(&cmd->stop_arg, 0);
-       }
 
        if (err)
                return 3;
@@ -1003,12 +1001,10 @@ static int usbdux_ao_cmdtest(struct comedi_device *dev,
 
        err |= cfc_check_trigger_arg_is(&cmd->scan_end_arg, cmd->chanlist_len);
 
-       if (cmd->stop_src == TRIG_COUNT) {
-               /* any count is allowed */
-       } else {
-               /* TRIG_NONE */
+       if (cmd->stop_src == TRIG_COUNT)
+               err |= cfc_check_trigger_arg_min(&cmd->stop_arg, 1);
+       else    /* TRIG_NONE */
                err |= cfc_check_trigger_arg_is(&cmd->stop_arg, 0);
-       }
 
        if (err)
                return 3;