rtc: Fix UBSAN overflow warning

Users may call 'ioctl' and pass a very big value on 'tm->tm_year'.
It can be overflowed in 'int' after add 1900.
In function 'rtc_month_days' and 'mktime64', also treated it as an
'unsigned' parameter.

UBSAN: Undefined behaviour in drivers/rtc/rtc-lib.c:103:59
signed integer overflow:
2147483647 + 1900 cannot be represented in type 'int'

UBSAN: Undefined behaviour in drivers/rtc/rtc-lib.c:119:30
signed integer overflow:
2147483647 + 1900 cannot be represented in type 'int'

So, covert it to 'unsigned' explicitly.

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/lib.c b/drivers/rtc/lib.c
index ef160da842200c91712052f3368e33158f0607e9..9714cb3d1e29816884557d7696bb20b5d7c3a986 100644 (file)
--- a/drivers/rtc/lib.c
+++ b/drivers/rtc/lib.c
@@ -100,7 +100,7 @@ int rtc_valid_tm(struct rtc_time *tm)
        if (tm->tm_year < 70
                || ((unsigned)tm->tm_mon) >= 12
                || tm->tm_mday < 1
-               || tm->tm_mday > rtc_month_days(tm->tm_mon, tm->tm_year + 1900)
+               || tm->tm_mday > rtc_month_days(tm->tm_mon, ((unsigned)tm->tm_year + 1900))
                || ((unsigned)tm->tm_hour) >= 24
                || ((unsigned)tm->tm_min) >= 60
                || ((unsigned)tm->tm_sec) >= 60)
@@ -116,8 +116,8 @@ EXPORT_SYMBOL(rtc_valid_tm);
  */
 time64_t rtc_tm_to_time64(struct rtc_time *tm)
 {
-       return mktime64(tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday,
-                       tm->tm_hour, tm->tm_min, tm->tm_sec);
+       return mktime64(((unsigned)tm->tm_year + 1900), tm->tm_mon + 1,
+                       tm->tm_mday, tm->tm_hour, tm->tm_min, tm->tm_sec);
 }
 EXPORT_SYMBOL(rtc_tm_to_time64);