{
  "cveId": "CVE-2026-98818",
  "url": "https://patchblox.com/security/cve/CVE-2026-98818",
  "summary": "CVE-2026-98818 is fixed in linux on 1 platform by DEBIAN-CVE-2026-98818 (version 7.2.10-1), released October 19, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "mm/slab: do not wake up kswapd in __kfree_rcu_sheaf()",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  mm/slab: do not wake up kswapd in __kfree_rcu_sheaf()  Since kfree_rcu() can be called under pi_lock (a raw spinlock in the scheduler), kfree_rcu() itself should never allocate memory with __GFP_KSWAPD_RECLAIM as waking up kswapd ends up acquiring pi_lock, which leads to a deadlock.  Reproducing the issue even intentionally was not straightforward. The set_cpus_allowed_force() path that is called under pi_lock is exercised very rarely, and competing tasks that allocate memory will most likely wake kswapd up.  Therefore the existence of the deadlock was verified with a modified kernel that has a lockdep map for waking up kswapd:    ======================================================   WARNING: possible circular locking dependency detected   7.2.0-rc1-slab-for-next\u002B #10 Not tainted   ------------------------------------------------------   git/6660 is trying to acquire lock:   ffff8e524533c550 (\u0026p-\u003Epi_lock){-.-.}-{2:2}, at: _raw_spin_lock_irqsave\u002B0x12/0x20    but task is already holding lock:   ffff8e57bffff1a0 (\u0026pgdat-\u003Ekswapd_wait){....}-{3:3}, at: _raw_spin_lock_irqsave\u002B0x12/0x20    which lock already depends on the new lock.    the existing dependency chain (in reverse order) is:    -\u003E #2 (\u0026pgdat-\u003Ekswapd_wait){....}-{3:3}:          __lock_acquire\u002B0x5a4/0xc50          lock_acquire.part.0\u002B0xb7/0x240          lock_acquire\u002B0x70/0x170          __raw_spin_lock_irqsave\u002B0x44/0x80          _raw_spin_lock_irqsave\u002B0x12/0x20          __wake_up_common_lock\u002B0x31/0xa0          __wake_up\u002B0x20/0x40          kswapd_wakeup_wake\u002B0x7e/0x110          wakeup_kswapd\u002B0x295/0x320          wake_all_kswapds\u002B0xac/0x1a0          __alloc_pages_slowpath.constprop.0\u002B0x282/0xf80          __alloc_frozen_pages_noprof\u002B0x32a/0x360          alloc_slab_page\u002B0x2e/0x160          allocate_slab\u002B0x82/0x420          new_slab\u002B0x52/0xb0          refill_objects\u002B0x13d/0x190          refill_sheaf\u002B0x5d/0xd0          __pcs_replace_empty_main\u002B0x230/0xb10          [...]    -\u003E #1 (kswapd_wakeup){-.-.}-{0:0}:          __lock_acquire\u002B0x5a4/0xc50          lock_sync.part.0\u002B0x75/0x100          lock_sync\u002B0x36/0x70          might_wakeup_kswapd\u002B0x61/0xa0          __kfree_rcu_sheaf\u002B0x33/0xd90          kvfree_call_rcu\u002B0x1d4/0x3b0          set_cpus_allowed_force\u002B0x163/0x220          cpuset_cpus_allowed_fallback\u002B0x18b/0x240          select_fallback_rq\u002B0x1e6/0x250 \t [...]    -\u003E #0 (\u0026p-\u003Epi_lock){-.-.}-{2:2}:          check_prev_add\u002B0xe6/0xe00          validate_chain\u002B0x51e/0x6e0          __lock_acquire\u002B0x5a4/0xc50          lock_acquire.part.0\u002B0xb7/0x240          lock_acquire\u002B0x70/0x170          __raw_spin_lock_irqsave\u002B0x44/0x80          _raw_spin_lock_irqsave\u002B0x12/0x20          try_to_wake_up\u002B0x77/0xa90          default_wake_function\u002B0x27/0x60          autoremove_wake_function\u002B0x23/0xb0          __wake_up_common\u002B0xb8/0x170          __wake_up_common_lock\u002B0x51/0xa0          __wake_up\u002B0x20/0x40          kswapd_wakeup_wake\u002B0x7e/0x110          wakeup_kswapd\u002B0x295/0x320          wake_all_kswapds\u002B0xac/0x1a0          __alloc_pages_slowpath.constprop.0\u002B0x282/0xf80          __alloc_frozen_pages_noprof\u002B0x32a/0x360          alloc_slab_page\u002B0x2e/0x160          allocate_slab\u002B0x82/0x420          new_slab\u002B0x52/0xb0          refill_objects\u002B0x13d/0x190          refill_sheaf\u002B0x5d/0xd0          __pcs_replace_empty_main\u002B0x230/0xb10          [...]    other info that might help us debug this:    Chain exists of:     \u0026p-\u003Epi_lock --\u003E kswapd_wakeup --\u003E \u0026pgdat-\u003Ekswapd_wait     Possible unsafe locking scenario:           CPU0                    CPU1          ----                    ----     lock(\u0026pgdat-\u003Ekswapd_wait);                                  lock(kswapd_wakeup);                                  lock(\u0026pgdat-\u003Ekswapd_wait);     lock(\u0026p-\u003Epi_lock);     *** DEADLOCK ***    3 locks held by git/6660:    #0: ffff8e519f0e9e20 (\u0026type-\u003Ei_mutex_dir_key#6){\u002B\u002B\u002B\u002B}-{4:4}, at: lookup_slow\u002B0x2d/0x60    #1: ffffffff8a31c460 (kswapd_wakeup){-.-.}- ---truncated---",
  "published": "2026-10-18T16:17:36Z",
  "severity": "",
  "epss": 0.00162,
  "epssPercentile": 0.05473,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98818",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.10-1",
      "fix": "DEBIAN-CVE-2026-98818",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98818",
      "released": "2026-10-19T16:27:52Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T13:31:49Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}