UBUNTU-CVE-2026-89759: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: mm/kmemleak: avoid soft lockup when scanning task stacks Patch series "mm/kmemleak: avoid soft lockup when scanning task", v3. kmemleakscan() scans every task stack under one rcureadlock() with no reschedule point, which can trip the soft lockup watchdog on hosts with very many threads. That prints the following message, depending on the workload+host configuration: watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537] scanblock kmemleakscan kmemleakscanthread kthread Patch 1 walks the tasks with findgepid() so the scan reschedules between tasks Patches 2-3 let the scan loops stop early once a scan is interrupted. This patch (of 3): kmemleakscan() walks every thread and scans its kernel stack under a single rcureadlock() with no reschedule point. On a host with very many threads -- amplified by KASAN/lockdep in debug builds -- this loop can hog a CPU long enough to trip the soft lockup watchdog: watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537] scanblock kmemleakscan kmemleakscanthread kthread A condresched() cannot be added directly: the loop runs inside an RCU read-side critical section. Walk the tasks one PID at a time with findgepid(), taking the RCU read lock only to look up and pin each task. The stack is then scanned with no lock held, so condresched() runs between tasks and the scan stops early on scanshouldstop(). This follows the nexttgid()/taskseqgetnext() iteration pattern and keeps each RCU critical section short.