CVE-2026-68165

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/core: validate ranges in damonsetregions()

DAMON core logic assumes zero length regions don't exist. However, a few DAMON API callers including DAMONSYSFS, DAMONRECLAIM and DAMONLRUSORT allow users to set empty monitoring target regions. This could result in WARNONCE() on CONFIGDAMONDEBUGSANITY enabled kernel, and divide-by-zero from damonmergetwo_regions().

For example, the WANR_ONCE() can be triggered like below.

# grep DAMON_DEBUG_SANITY /boot/config-$(uname -r)
# CONFIG_DAMON_DEBUG_SANITY=y
# damo start
# cd /sys/kernel/mm/damon/admin/kdamonds/0
# echo 0 > contexts/0/targets/0/regions/0/start
# echo 0 > contexts/0/targets/0/regions/0/end
# echo commit > state
# dmesg
[....]
[   73.705780] ------------[ cut here ]------------
[   73.707552] start 0 >= end 0
[   73.708452] WARNING: mm/damon/core.c:359 at damon_new_region+0x6e/0x80, CPU#1: kdamond.0/758
[...]

All DAMON API callers eventually use damonsetregions() to setup the regions. Add the validation logic in the function.