On Sat, Apr 24, 2021 at 01:12:46AM +0300, Andy Shevchenko wrote:
> On Friday, April 23, 2021, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> > Hello Karol Wrona,
> >
> > The patch 50dd64d57eee: "iio: common: ssp_sensors: Add sensorhub
> > driver" from Jan 28, 2015, leads to the following static checker
> > warning:
> >
> > drivers/iio/common/ssp_sensors/ssp_spi.c:276 ssp_parse_dataframe()
> > warn: check that incremented offset 'idx' is capped
> >
> > drivers/iio/common/ssp_sensors/ssp_spi.c
> > 267 static int ssp_parse_dataframe(struct ssp_data *data, char
> > *dataframe, int len)
> > 268 {
> > 269 int idx, sd;
> > 270 struct ssp_sensor_data *spd;
> > 271 struct iio_dev **indio_devs = data->sensor_devs;
> > 272
> > 273 for (idx = 0; idx < len;) {
> > 274 switch (dataframe[idx++]) {
> > 275 case SSP_MSG2AP_INST_BYPASS_DATA:
> >
> > There needs to be be a check here:
> >
> > if (idx == len)
> > return -EPROTO;
> >
> > 276 sd = dataframe[idx++];
> > 277 if (sd < 0 || sd >= SSP_SENSOR_MAX) {
> > 278 dev_err(SSP_DEV,
> > 279 "Mcu data frame1 error
> > %d\n", sd);
> > 280 return -EPROTO;
> > 281 }
> > 282
> > 283 if (indio_devs[sd]) {
> > 284 spd = iio_priv(indio_devs[sd]);
> > 285 if (spd->process_data)
> > 286
> > spd->process_data(indio_devs[sd],
> > 287
> > &dataframe[idx],
> > 288
> > data->timestamp);
> >
> > But then the problem is we don't pass the "len" to ->process_data(). I
> > looked at trying to fix this but it's a bit involved.
>
>
> Because infinite loops are bad. That’s why I try convince people to avoid
> them as much as possible.
>
I'm not sure what you mean at all. The issue here is that
->process_data() reads an unknown number of bytes. We need to pass
"len - idx" to ->process_data() to detect the overflow and return -EPROTO.
regards,
dan carpenter
>
> >
> > 289 } else {
> > 290 dev_err(SSP_DEV, "no client for
> > frame\n");
> > 291 }
> > 292
> > 293 idx += ssp_offset_map[sd];
> > 294 break;
> > 295 case SSP_MSG2AP_INST_DEBUG_DATA:
> > 296 sd = ssp_print_mcu_debug(dataframe, &idx,
> > len);
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > There is another potential read overflow here because we read one more
> > byte before we check the "len".
> >
> > 297 if (sd) {
> > 298 dev_err(SSP_DEV,
> > 299 "Mcu data frame3 error
> > %d\n", sd);
> > 300 return sd;
> > 301 }
> > 302 break;
> > 303 case SSP_MSG2AP_INST_LIBRARY_DATA:
> > 304 idx += len;
> > 305 break;
> > 306 case SSP_MSG2AP_INST_BIG_DATA:
> > 307 ssp_handle_big_data(data, dataframe, &idx);
> > 308 break;
> > 309 case SSP_MSG2AP_INST_TIME_SYNC:
> > 310 data->time_syncing = true;
> > 311 break;
> > 312 case SSP_MSG2AP_INST_RESET:
> > 313 ssp_queue_ssp_refresh_task(data, 0);
> > 314 break;
> > 315 }
> > 316 }
> > 317
> > 318 if (data->time_syncing)
> > 319 data->timestamp = ktime_get_real_ns();
> > 320
> > 321 return 0;
> > 322 }
> >
> > regards,
> > dan carpenter
> >
>
>
> --
> With Best Regards,
> Andy Shevchenko
