[PATCH 3.16 047/129] rtc: ds1672: fix unintended sign extension

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

commit f0c04c276739ed8acbb41b4868e942a55b128dca upstream.

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@xxxxxxxxxxxxx>
Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/rtc/rtc-ds1672.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/rtc/rtc-ds1672.c
+++ b/drivers/rtc/rtc-ds1672.c
@@ -60,7 +60,8 @@ static int ds1672_get_datetime(struct i2
 		"%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);