mm/kmemleak: avoid soft lockup when scanning task stacks

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Summary

CVECVE-2026-89759
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:20:06 UTC
Updated2026-10-21 13:20:25 UTC
DescriptionIn 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. kmemleak_scan() scans every task stack under one rcu_read_lock() 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] scan_block kmemleak_scan kmemleak_scan_thread kthread Patch 1 walks the tasks with find_ge_pid() so the scan reschedules between tasks Patches 2-3 let the scan loops stop early once a scan is interrupted. This patch (of 3): kmemleak_scan() walks every thread and scans its kernel stack under a single rcu_read_lock() 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] scan_block kmemleak_scan kmemleak_scan_thread kthread A cond_resched() cannot be added directly: the loop runs inside an RCU read-side critical section. Walk the tasks one PID at a time with find_ge_pid(), taking the RCU read lock only to look up and pin each task. The stack is then scanned with no lock held, so cond_resched() runs between tasks and the scan stops early on scan_should_stop(). This follows the next_tgid()/task_seq_get_next() iteration pattern and keeps each RCU critical section short.

Risk And Classification

EPSS: 0.001860000 probability, percentile 0.083730000 (date 2026-09-14)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected c4b28963fd79457315783b3b0f21c01eb88cfdc1 f1cd6c4c35243377882c47236281d03ee3be6eeb git Not specified
CNA Linux Linux affected c4b28963fd79457315783b3b0f21c01eb88cfdc1 9a1b12c06c192290b8479de48f66f1e75d89c4b7 git Not specified
CNA Linux Linux affected c4b28963fd79457315783b3b0f21c01eb88cfdc1 3fc8044251de21555fb02c365fa681bab8b0db55 git Not specified
CNA Linux Linux affected c4b28963fd79457315783b3b0f21c01eb88cfdc1 1838c704bcb4fd3556cf67513c6f97a39099e35c git Not specified
CNA Linux Linux affected c4b28963fd79457315783b3b0f21c01eb88cfdc1 5d10d4e19e6daa487f0cd0ea6cba472325de92f9 git Not specified
CNA Linux Linux affected 5.10 Not specified
CNA Linux Linux unaffected 5.10 semver Not specified
CNA Linux Linux unaffected 6.6.160 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/9a1b12c06c192290b8479de48f66f1e75d89c4b7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f1cd6c4c35243377882c47236281d03ee3be6eeb 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/5d10d4e19e6daa487f0cd0ea6cba472325de92f9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3fc8044251de21555fb02c365fa681bab8b0db55 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1838c704bcb4fd3556cf67513c6f97a39099e35c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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