Fix stack corruption of zeroing too much in bf1 driver.
diff --git a/driver-bitfury.c b/driver-bitfury.c
index a54723a..fb6d44a 100644
--- a/driver-bitfury.c
+++ b/driver-bitfury.c
@@ -576,7 +576,7 @@ static int64_t bf1_scan(struct thr_info *thr, struct cgpu_info *bitfury,
&amount, ms_diff, C_BF1_GETRES);
total += amount;
while (amount) {
- usb_read_once_timeout(bitfury, readbuf + total, 512, &amount, 10,
+ usb_read_once_timeout(bitfury, readbuf + total, 512 - total, &amount, 10,
C_BF1_GETRES);
total += amount;
};