Commit 627b771b authored Jan 20, 2020 by Wen Yang Committed by Greg Kroah-Hartman Oct 01, 2020

timekeeping: Prevent 32bit truncation in scale64_check_overflow()



[ Upstream commit 4cbbc3a0eeed675449b1a4d080008927121f3da3 ]

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>

parent 1ee3da6b

kernel/time/timekeeping.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -1004,9 +1004,8 @@ 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;
		}