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rtc: ds1672: fix unintended sign extension

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[ Upstream commit f0c04c2767 ]

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: edf1aaa31f ("[PATCH] RTC subsystem: DS1672 driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Colin Ian King
2019-02-05 18:04:49 +00:00
committed by Chris
parent e35c6f21ce
commit 1bffeaeef1
1 changed files with 2 additions and 1 deletions
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3
drivers/rtc/rtc-ds1672.c
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@@ -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);