From: Wen Yang <wenyang@linux.alibaba.com> mainline inclusion from mainline-5.5-rc7 commit d3ac946ec9de10ec4b9718ad30703c5e077916a1 category: bugfix bugzilla: 28317 CVE: NA ------------------------------------------------- The two variables 'numerator' and 'denominator', though they are declared as long, they should actually be unsigned long (according to the implementation of the fprop_fraction_percpu() function) And do_div() does a 64-by-32 division, while the divisor 'denominator' is unsigned long, thus 64-bit on 64-bit platforms. Hence the proper function to call is div64_ul(). Link: http://lkml.kernel.org/r/20200102081442.8273-3-wenyang@linux.alibaba.com Signed-off-by: Wen Yang <wenyang@linux.alibaba.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Qian Cai <cai@lca.pw> Cc: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> (cherry picked from commit d3ac946ec9de10ec4b9718ad30703c5e077916a1) Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Reviewed-by: Jing Xiangfeng <jingxiangfeng@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- mm/page-writeback.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 078f146..566df02 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -765,7 +765,7 @@ static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) struct wb_domain *dom = dtc_dom(dtc); unsigned long thresh = dtc->thresh; u64 wb_thresh; - long numerator, denominator; + unsigned long numerator, denominator; unsigned long wb_min_ratio, wb_max_ratio; /* @@ -776,7 +776,7 @@ static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100; wb_thresh *= numerator; - do_div(wb_thresh, denominator); + wb_thresh = div64_ul(wb_thresh, denominator); wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); -- 1.8.3