Hello Robert Eshleman,
Commit 6aef699a7d7e ("iio: light: add driver for MAX44009") from Jan
31, 2019 (linux-next), leads to the following Smatch static checker
warning:
drivers/iio/light/max44009.c:309 max44009_threshold_byte_from_fraction()
warn: potential integer overflow 'integral * 1000' 's32min-7520256 * 1000'
drivers/iio/light/max44009.c
299 static int max44009_threshold_byte_from_fraction(int integral, int fractional)
300 {
301 int mantissa, exp;
302
303 if ((integral <= 0 && fractional <= 0) ||
I don't understand how negatives are handled here. Was || intended
instead of &&? These values come from the user via
iio_ev_value_store().
304 integral > MAX44009_MAXIMUM_THRESHOLD ||
305 (integral == MAX44009_MAXIMUM_THRESHOLD && fractional != 0))
306 return -EINVAL;
307
308 /* Reverse scaling of fixed-point integral */
--> 309 mantissa = integral * MAX44009_SCALE_DENOMINATOR;
If integral were INT_MIN and fractional were any positive value then
this multiply would result in a integer wrapping bug.
310 mantissa /= MAX44009_SCALE_NUMERATOR;
311
312 /* Reverse scaling of fixed-point fractional */
313 mantissa += fractional / MAX44009_FRACT_MULT *
314 (MAX44009_SCALE_DENOMINATOR / MAX44009_SCALE_NUMERATOR);
315
316 for (exp = 0; mantissa > 0xff; exp++)
317 mantissa >>= 1;
318
319 mantissa >>= 4;
320 mantissa &= 0xf;
321 exp <<= 4;
322
323 return exp | mantissa;
324 }
regards,
dan carpenter
