CVE-2026-89759 (GCVE-0-2026-89759)
Vulnerability from cvelistv5
Published
2026-09-11 19:47
Modified
2026-10-21 12:48
Severity ?
Summary
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. 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.
References
Impacted products
Vendor Product Version
Linux Linux Version: c4b28963fd79457315783b3b0f21c01eb88cfdc1
Version: c4b28963fd79457315783b3b0f21c01eb88cfdc1
Version: c4b28963fd79457315783b3b0f21c01eb88cfdc1
Version: c4b28963fd79457315783b3b0f21c01eb88cfdc1
Version: c4b28963fd79457315783b3b0f21c01eb88cfdc1
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{
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/kmemleak: avoid soft lockup when scanning task stacks\n\nPatch series \"mm/kmemleak: avoid soft lockup when scanning task\", v3.\n\nkmemleak_scan() scans every task stack under one rcu_read_lock() with no\nreschedule point, which can trip the soft lockup watchdog on hosts with\nvery many threads.\n\nThat prints the following message, depending on the workload+host\nconfiguration:\n\n      watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537]\n       scan_block\n       kmemleak_scan\n       kmemleak_scan_thread\n       kthread\n\nPatch 1 walks the tasks with find_ge_pid() so the scan reschedules between\ntasks\n\nPatches 2-3 let the scan loops stop early once a scan is interrupted.\n\n\nThis patch (of 3):\n\nkmemleak_scan() walks every thread and scans its kernel stack under a\nsingle rcu_read_lock() with no reschedule point.  On a host with very many\nthreads -- amplified by KASAN/lockdep in debug builds -- this loop can hog\na CPU long enough to trip the soft lockup watchdog:\n\n  watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [kmemleak:537]\n   scan_block\n   kmemleak_scan\n   kmemleak_scan_thread\n   kthread\n\nA cond_resched() cannot be added directly: the loop runs inside an RCU\nread-side critical section.\n\nWalk the tasks one PID at a time with find_ge_pid(), taking the RCU read\nlock only to look up and pin each task.  The stack is then scanned with no\nlock held, so cond_resched() runs between tasks and the scan stops early\non scan_should_stop().  This follows the next_tgid()/task_seq_get_next()\niteration pattern and keeps each RCU critical section short."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T12:48:36.907Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f1cd6c4c35243377882c47236281d03ee3be6eeb"
        },
        {
          "url": "https://git.kernel.org/stable/c/9a1b12c06c192290b8479de48f66f1e75d89c4b7"
        },
        {
          "url": "https://git.kernel.org/stable/c/3fc8044251de21555fb02c365fa681bab8b0db55"
        },
        {
          "url": "https://git.kernel.org/stable/c/1838c704bcb4fd3556cf67513c6f97a39099e35c"
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        {
          "url": "https://git.kernel.org/stable/c/5d10d4e19e6daa487f0cd0ea6cba472325de92f9"
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      "title": "mm/kmemleak: avoid soft lockup when scanning task stacks",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89759",
    "datePublished": "2026-09-11T19:47:01.313Z",
    "dateReserved": "2026-09-11T19:38:34.763Z",
    "dateUpdated": "2026-10-21T12:48:36.907Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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