CVE-2026-89756 is a vulnerability in Linux Kernel
Published on September 11, 2026
mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()
In the Linux kernel, the following vulnerability has been resolved:
mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch()
migrate_pages_batch() unmaps each folio before moving it, and every
unmap runs the mmu_notifier invalidate callbacks. On KVM hosts
try_to_migrate() ends up in kvm_mmu_notifier_invalidate_range_start() ->
tdp_mmu_zap_leafs(), which is expensive, so unmapping a large batch keeps
the CPU busy for a long time.
The loop already calls cond_resched(), but on PREEMPTION kernels that is
a no-op, and involuntary preemption is not a Tasks-RCU quiescent state.
A long batch therefore never reports a quiescent state, and the
migrating task (e.g. kcompactd) becomes a Tasks-RCU holdout, stalling the
Tasks-RCU grace period for minutes, which is common at Meta fleet:
INFO: rcu_tasks detected stalls on tasks:
0000000055349ecc: .. nvcsw: 1157401/1157401 holdout: 1 idle_cpu: -1/56 task:kcompactd0 state:R running task
Call Trace:
tdp_mmu_zap_leafs
tdp_mmu_next_root
gfn_to_pfn_cache_invalidate_start
kvm_mmu_notifier_invalidate_range_start
__mmu_notifier_invalidate_range_start
try_to_migrate_one
try_to_migrate
migrate_pages_batch
migrate_pages
compact_zone
compact_node
kcompactd
kthread
Use cond_resched_tasks_rcu_qs() so a quiescent state is reported even
when cond_resched() does nothing.
This has also been discussed at [1]
Products Associated with CVE-2026-89756
Want to know whenever a new CVE is published for Linux Kernel? stack.watch will email you.
Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 4996a7bc01ef35570664854dac2530c604981039 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 5dc0daff0341c6baba19c38f47d299ac831d7e99 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 66734981b4d3c105223a13c827c9c73be18d91ad is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below efe8f86c0916f0f74eea74ae21a3b37f728c6bad is affected.
- Before 6.12.109 is affected.
- Before 6.18.50 is affected.
- Before 7.2.4 is affected.
- Version 6.12.109, <= 6.12.* is unaffected.
- Version 6.18.50, <= 6.18.* is unaffected.
- Version 7.2.4, <= 7.2.* is unaffected.
- Version 7.3-rc1, <= * is unaffected.