ntp: Fix integer overflow when setting time

commit a078c6d0 upstream.

'long secs' is passed as divisor to div_s64, which accepts a 32bit
divisor. On 64bit machines that value is trimmed back from 8 bytes
back to 4, causing a divide by zero when the number is bigger than
(1 << 32) - 1 and all 32 lower bits are 0.

Use div64_long() instead.
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Cc: johnstul@us.ibm.com
Link: http://lkml.kernel.org/r/1331829374-31543-2-git-send-email-levinsasha928@gmail.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[WT: div64_long() does not exist on 2.6.32 and needs a deeper backport than
 desired. Instead, address the issue by controlling that the divisor is
 correct for use as an s32 divisor]
Signed-off-by: Willy Tarreau <w@1wt.eu>

kernel/time/ntp.c

@@ -106,7 +106,7 @@ static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 {
 	time_status &= ~STA_MODE;
 
-	if (secs < MINSEC)
+	if ((s32)secs < MINSEC)
 		return 0;
 
 	if (!(time_status & STA_FLL) && (secs <= MAXSEC))