staging: comedi: comedi_test: limit maximum convert_arg

When testing the parameters for setting up an asynchronous command on
the AI subdevice, limit the maximum conversion period
(`cmd->convert_arg`) so that the number of conversions in a scan
(`cmd->scan_end_arg`, same as `cmd->chanlist_len`) multiplied by the
conversion period fits within an `unsigned int`, as that is used to
limit the minimum scan period (`cmd->scan_begin_arg`).

Also ensure rounding of the conversion period and scan period to the
nearest microsecond both fit in an `unsigned int`.  Do all this in stage
4 ("fix up any arguments") of the command testing.

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

diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c
index d9810caae4759ea7759177b192d5855fdb218d31..f011fbd2fd96f91095ef40be776ab6b549889a18 100644 (file)
--- a/drivers/staging/comedi/drivers/comedi_test.c
+++ b/drivers/staging/comedi/drivers/comedi_test.c
@@ -234,7 +234,7 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
                               struct comedi_cmd *cmd)
 {
        int err = 0;
-       unsigned int arg;
+       unsigned int arg, limit;
 
        /* Step 1 : check if triggers are trivially valid */
 
@@ -265,16 +265,8 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
        if (cmd->convert_src == TRIG_NOW)
                err |= comedi_check_trigger_arg_is(&cmd->convert_arg, 0);
 
-       if (cmd->scan_begin_src == TRIG_TIMER) {
-               err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
-                                                   NSEC_PER_USEC);
-               if (cmd->convert_src == TRIG_TIMER) {
-                       err |= comedi_check_trigger_arg_min(&cmd->
-                                                           scan_begin_arg,
-                                                           cmd->convert_arg *
-                                                           cmd->chanlist_len);
-               }
-       }
+       err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
+                                           NSEC_PER_USEC);
 
        err |= comedi_check_trigger_arg_min(&cmd->chanlist_len, 1);
        err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
@@ -290,21 +282,29 @@ static int waveform_ai_cmdtest(struct comedi_device *dev,
 
        /* step 4: fix up any arguments */
 
-       if (cmd->scan_begin_src == TRIG_TIMER) {
-               arg = cmd->scan_begin_arg;
-               /* round to nearest microsec */
-               arg = NSEC_PER_USEC *
-                     ((arg + (NSEC_PER_USEC / 2)) / NSEC_PER_USEC);
-               err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);
-       }
        if (cmd->convert_src == TRIG_TIMER) {
+               /* round convert_arg to nearest microsecond */
                arg = cmd->convert_arg;
-               /* round to nearest microsec */
-               arg = NSEC_PER_USEC *
-                     ((arg + (NSEC_PER_USEC / 2)) / NSEC_PER_USEC);
+               arg = min(arg,
+                         rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
+               arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
+               /* limit convert_arg to keep scan_begin_arg in range */
+               limit = UINT_MAX / cmd->scan_end_arg;
+               limit = rounddown(limit, (unsigned int)NSEC_PER_SEC);
+               arg = min(arg, limit);
                err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg);
        }
 
+       /* round scan_begin_arg to nearest microsecond */
+       arg = cmd->scan_begin_arg;
+       arg = min(arg, rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
+       arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
+       if (cmd->convert_src == TRIG_TIMER) {
+               /* but ensure scan_begin_arg is large enough */
+               arg = max(arg, cmd->convert_arg * cmd->scan_end_arg);
+       }
+       err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);
+
        if (err)
                return 4;