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>

1 files changed, 21 insertions, 21 deletions

diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c
index d9810caae475..f011fbd2fd96 100644
--- 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;