On 09.01.25 07:34, Stefan Roesch wrote:
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_ratio 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> --- Changes in V3: - Used long instead of unsigned long for min_ratio / max_ratio Changes in V2: - check for -EINVAL in bdi_set_min_bytes() - check for -EINVAL in bdi_set_max_bytes() --- mm/page-writeback.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index d213ead95675..d9861e42b2bd 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)
Note that I suggested returning "long" here, but it should also work as is. Acked-by: David Hildenbrand <david@xxxxxxxxxx> -- Cheers, David / dhildenb
