During testing it has been detected, that it is possible to get div by zero error in bdi_set_min_bytes. The error is caused by the function bdi_ratio_from_pages(). bdi_ratio_from_pages() calls global_dirty_limits. If the dirty threshold is 0, the div by zero is raised. This can happen if the root user is setting: echo 0 > /proc/sys/vm/dirty_ration. The following is a test case: echo 0 > /proc/sys/vm/dirty_ratio cd /sys/class/bdi/<device> echo 1 > strict_limit echo 8192 > min_bytes ==> error is raised. The problem is addressed by returning -EINVAL if dirty_ratio or dirty_bytes is set to 0. Reported-by: cheung wall <zzqq0103.hey@xxxxxxxxx> Closes: https://lore.kernel.org/linux-mm/87pll35yd0.fsf@xxxxxxxxxxxx/T/#t Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx> --- mm/page-writeback.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index d213ead95675..91aa7a5c0078 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -692,6 +692,8 @@ static unsigned long bdi_ratio_from_pages(unsigned long pages) unsigned long ratio; global_dirty_limits(&background_thresh, &dirty_thresh); + if (!dirty_thresh) + return -EINVAL; ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh); return ratio; base-commit: 0bc21e701a6ffacfdde7f04f87d664d82e8a13bf -- 2.47.1
