Executive brief
The Linux kernel's memory leak detection tool (kmemleak) can cause system performance degradation when scanning memory on hosts with many running processes. Without proper rescheduling during the scan, the system watchdog detects a potential freeze and reports an error, potentially disrupting operations on systems running memory leak detection.
Technical details
This vulnerability is a denial-of-service condition in the kernel's kmemleak subsystem where kmemleak_scan() iterates through all task stacks while holding an RCU read lock without a reschedule point. On systems with high thread counts (especially in debug builds with KASAN or lockdep enabled), the scanning loop monopolizes the CPU for extended periods, triggering the soft lockup watchdog. The fix restructures the iteration to walk tasks one PID at a time using find_ge_pid(), releasing the RCU lock between tasks and allowing cond_resched() to run, thus keeping RCU critical sections short and enabling early scan termination via scan_should_stop().
Affected products
- Linux Linux Kernel affected versions prior to patch
Timeline
- 2026-09-11: disclosed: CVE-2026-89759 published
- 2026-09-11: patched: Fix included in patch series resolving soft lockup condition