From 6242a0e06d60112686cac39c3f1bb4395c7e365f Mon Sep 17 00:00:00 2001 From: Wen Yang Date: Sat, 29 Aug 2020 15:51:00 +0800 Subject: [PATCH] timekeeping: Prevent 32bit truncation in scale64_check_overflow() mainline inclusion from mainline-v5.6 commit 4cbbc3a0eeed675449b1a4d080008927121f3da3 category: bugfix bugzilla: 32422 CVE: NA ------------------------ 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 Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200120100523.45656-1-wenyang@linux.alibaba.com Signed-off-by: Yang Yingliang Reviewed-by: Xiongfeng Wang Signed-off-by: Yang Yingliang --- kernel/time/timekeeping.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index d3b375591e61..64aa492f7942 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -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; } -- GitLab