CVE-2026-31457

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

mm/damon/sysfs: check contexts->nr in repeatcallfn

damonsysfsrepeatcallfn() calls damonsysfsupdtunedintervals(), damonsysfsupdschemesstats(), and damonsysfsupdschemeseffectivequotas() without checking contexts->nr. If nrcontexts is set to 0 via sysfs while DAMON is running, these functions dereference contexts_arr[0] and cause a NULL pointer dereference. Add the missing check.

For example, the issue can be reproduced using DAMON sysfs interface and DAMON user-space tool (damo) [1] like below.

$ sudo damo start --refresh_interval 1s
$ echo 0 | sudo tee \
        /sys/kernel/mm/damon/admin/kdamonds/0/contexts/nr_contexts