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timekeeping: Prevent 32bit truncation in scale64_check_overflow() 

[ Upstream commit 4cbbc3a0ee ]

While unlikely the divisor in scale64_check_overflow() could be >= 32bit in
scale64_check_overflow(). do_div() truncates the divisor to 32bit at least
on 32bit platforms.

Use div64_u64() instead to avoid the truncation to 32-bit.

[ tglx: Massaged changelog ]

Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200120100523.45656-1-wenyang@linux.alibaba.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
Wen Yang 2020-01-20 18:05:23 +08:00 committed by Greg Kroah-Hartman
parent 202e2ff9de
commit efc95f2ef7
1 changed files with 1 additions and 2 deletions
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kernel/time/timekeeping.c
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@ -1005,9 +1005,8 @@ static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
return -EOVERFLOW;
tmp *= mult;
rem *= mult;
do_div(rem, div);
rem = div64_u64(rem * mult, div);
*base = tmp + rem;
return 0;
}