rtc: ds1672: fix unintended sign extension

Shifting a u8 by 24 will cause the value to be promoted to an integer. If
the top bit of the u8 is set then the following conversion to an unsigned
long will sign extend the value causing the upper 32 bits to be set in
the result.

Fix this by casting the u8 value to an unsigned long before the shift.

Detected by CoverityScan, CID#138801 ("Unintended sign extension")

Fixes: edf1aaa31fc5 ("[PATCH] RTC subsystem: DS1672 driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-ds1672.c b/drivers/rtc/rtc-ds1672.c
index 9caaccccaa575f41fb3280f3753d8dea8ec3c9db..b1ebca099b0dffb064d59c8dfa8821f55374f48c 100644 (file)
--- a/drivers/rtc/rtc-ds1672.c
+++ b/drivers/rtc/rtc-ds1672.c
@@ -58,7 +58,8 @@ static int ds1672_get_datetime(struct i2c_client *client, struct rtc_time *tm)
                "%s: raw read data - counters=%02x,%02x,%02x,%02x\n",
                __func__, buf[0], buf[1], buf[2], buf[3]);
 
-       time = (buf[3] << 24) | (buf[2] << 16) | (buf[1] << 8) | buf[0];
+       time = ((unsigned long)buf[3] << 24) | (buf[2] << 16) |
+              (buf[1] << 8) | buf[0];
 
        rtc_time_to_tm(time, tm);