[ 051/175] ntp: Fix integer overflow when setting time

From: Greg KH
Date: Fri Mar 30 2012 - 17:19:41 EST


3.3-stable review patch. If anyone has any objections, please let me know.

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

From: Sasha Levin <levinsasha928@xxxxxxxxx>

commit a078c6d0e6288fad6d83fb6d5edd91ddb7b6ab33 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@xxxxxxxxx>
Cc: johnstul@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1331829374-31543-2-git-send-email-levinsasha928@xxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/time/ntp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -275,7 +275,7 @@ static inline s64 ntp_update_offset_fll(

time_status |= STA_MODE;

- return div_s64(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
+ return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
}

static void ntp_update_offset(long offset)


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