CVE-2025-68169 (GCVE-0-2025-68169)

Vulnerability from cvelistv5 – Published: 2025-12-16 13:42 – Updated: 2026-05-11 21:47
VLAI
Title
netpoll: Fix deadlock in memory allocation under spinlock
Summary
In the Linux kernel, the following vulnerability has been resolved: netpoll: Fix deadlock in memory allocation under spinlock Fix a AA deadlock in refill_skbs() where memory allocation while holding skb_pool->lock can trigger a recursive lock acquisition attempt. The deadlock scenario occurs when the system is under severe memory pressure: 1. refill_skbs() acquires skb_pool->lock (spinlock) 2. alloc_skb() is called while holding the lock 3. Memory allocator fails and calls slab_out_of_memory() 4. This triggers printk() for the OOM warning 5. The console output path calls netpoll_send_udp() 6. netpoll_send_udp() attempts to acquire the same skb_pool->lock 7. Deadlock: the lock is already held by the same CPU Call stack: refill_skbs() spin_lock_irqsave(&skb_pool->lock) <- lock acquired __alloc_skb() kmem_cache_alloc_node_noprof() slab_out_of_memory() printk() console_flush_all() netpoll_send_udp() skb_dequeue() spin_lock_irqsave(&skb_pool->lock) <- deadlock attempt This bug was exposed by commit 248f6571fd4c51 ("netpoll: Optimize skb refilling on critical path") which removed refill_skbs() from the critical path (where nested printk was being deferred), letting nested printk being called from inside refill_skbs() Refactor refill_skbs() to never allocate memory while holding the spinlock. Another possible solution to fix this problem is protecting the refill_skbs() from nested printks, basically calling printk_deferred_{enter,exit}() in refill_skbs(), then, any nested pr_warn() would be deferred. I prefer this approach, given I _think_ it might be a good idea to move the alloc_skb() from GFP_ATOMIC to GFP_KERNEL in the future, so, having the alloc_skb() outside of the lock will be necessary step. There is a possible TOCTOU issue when checking for the pool length, and queueing the new allocated skb, but, this is not an issue, given that an extra SKB in the pool is harmless and it will be eventually used.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6664 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 248f6571fd4c51531f7f8f07f186f7ae98a50afc , < 06742a3ab884d7428c9050b205ffcf6a8a548397 (git)
Affected: 248f6571fd4c51531f7f8f07f186f7ae98a50afc , < 327c20c21d80e0d87834b392d83ae73c955ad8ff (git)
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Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (semver)
Unaffected: 6.17.8 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/core/netpoll.c"
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          "vendor": "Linux",
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                  "vulnerable": true
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetpoll: Fix deadlock in memory allocation under spinlock\n\nFix a AA deadlock in refill_skbs() where memory allocation while holding\nskb_pool-\u003elock can trigger a recursive lock acquisition attempt.\n\nThe deadlock scenario occurs when the system is under severe memory\npressure:\n\n1. refill_skbs() acquires skb_pool-\u003elock (spinlock)\n2. alloc_skb() is called while holding the lock\n3. Memory allocator fails and calls slab_out_of_memory()\n4. This triggers printk() for the OOM warning\n5. The console output path calls netpoll_send_udp()\n6. netpoll_send_udp() attempts to acquire the same skb_pool-\u003elock\n7. Deadlock: the lock is already held by the same CPU\n\nCall stack:\n  refill_skbs()\n    spin_lock_irqsave(\u0026skb_pool-\u003elock)    \u003c- lock acquired\n    __alloc_skb()\n      kmem_cache_alloc_node_noprof()\n        slab_out_of_memory()\n          printk()\n            console_flush_all()\n              netpoll_send_udp()\n                skb_dequeue()\n                  spin_lock_irqsave(\u0026skb_pool-\u003elock)     \u003c- deadlock attempt\n\nThis bug was exposed by commit 248f6571fd4c51 (\"netpoll: Optimize skb\nrefilling on critical path\") which removed refill_skbs() from the\ncritical path (where nested printk was being deferred), letting nested\nprintk being called from inside refill_skbs()\n\nRefactor refill_skbs() to never allocate memory while holding\nthe spinlock.\n\nAnother possible solution to fix this problem is protecting the\nrefill_skbs() from nested printks, basically calling\nprintk_deferred_{enter,exit}() in refill_skbs(), then, any nested\npr_warn() would be deferred.\n\nI prefer this approach, given I _think_ it might be a good idea to move\nthe alloc_skb() from GFP_ATOMIC to GFP_KERNEL in the future, so, having\nthe alloc_skb() outside of the lock will be necessary step.\n\nThere is a possible TOCTOU issue when checking for the pool length, and\nqueueing the new allocated skb, but, this is not an issue, given that\nan extra SKB in the pool is harmless and it will be eventually used."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T21:47:58.964Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/06742a3ab884d7428c9050b205ffcf6a8a548397"
        },
        {
          "url": "https://git.kernel.org/stable/c/327c20c21d80e0d87834b392d83ae73c955ad8ff"
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      "title": "netpoll: Fix deadlock in memory allocation under spinlock",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-68169",
    "datePublished": "2025-12-16T13:42:49.270Z",
    "dateReserved": "2025-12-16T13:41:40.250Z",
    "dateUpdated": "2026-05-11T21:47:58.964Z",
    "state": "PUBLISHED"
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      "date": "2026-10-16",
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      "percentile": "0.07694"
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                "product": "Linux",
                "programFiles": [
                  "net/core/netpoll.c"
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                "vendor": "Linux",
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                    "versionType": "git"
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetpoll: Fix deadlock in memory allocation under spinlock\n\nFix a AA deadlock in refill_skbs() where memory allocation while holding\nskb_pool-\u003elock can trigger a recursive lock acquisition attempt.\n\nThe deadlock scenario occurs when the system is under severe memory\npressure:\n\n1. refill_skbs() acquires skb_pool-\u003elock (spinlock)\n2. alloc_skb() is called while holding the lock\n3. Memory allocator fails and calls slab_out_of_memory()\n4. This triggers printk() for the OOM warning\n5. The console output path calls netpoll_send_udp()\n6. netpoll_send_udp() attempts to acquire the same skb_pool-\u003elock\n7. Deadlock: the lock is already held by the same CPU\n\nCall stack:\n  refill_skbs()\n    spin_lock_irqsave(\u0026skb_pool-\u003elock)    \u003c- lock acquired\n    __alloc_skb()\n      kmem_cache_alloc_node_noprof()\n        slab_out_of_memory()\n          printk()\n            console_flush_all()\n              netpoll_send_udp()\n                skb_dequeue()\n                  spin_lock_irqsave(\u0026skb_pool-\u003elock)     \u003c- deadlock attempt\n\nThis bug was exposed by commit 248f6571fd4c51 (\"netpoll: Optimize skb\nrefilling on critical path\") which removed refill_skbs() from the\ncritical path (where nested printk was being deferred), letting nested\nprintk being called from inside refill_skbs()\n\nRefactor refill_skbs() to never allocate memory while holding\nthe spinlock.\n\nAnother possible solution to fix this problem is protecting the\nrefill_skbs() from nested printks, basically calling\nprintk_deferred_{enter,exit}() in refill_skbs(), then, any nested\npr_warn() would be deferred.\n\nI prefer this approach, given I _think_ it might be a good idea to move\nthe alloc_skb() from GFP_ATOMIC to GFP_KERNEL in the future, so, having\nthe alloc_skb() outside of the lock will be necessary step.\n\nThere is a possible TOCTOU issue when checking for the pool length, and\nqueueing the new allocated skb, but, this is not an issue, given that\nan extra SKB in the pool is harmless and it will be eventually used."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnetpoll: Correcci\u00f3n de interbloqueo en la asignaci\u00f3n de memoria bajo spinlock\n\nCorrige un interbloqueo AA en refill_skbs() donde la asignaci\u00f3n de memoria mientras se mantiene skb_pool -\u003e lock puede desencadenar un intento de adquisici\u00f3n recursiva del bloqueo.\n\nEl escenario de interbloqueo ocurre cuando el sistema est\u00e1 bajo una presi\u00f3n de memoria severa:\n\n1. refill_skbs() adquiere skb_pool -\u003e lock (spinlock)\n2. alloc_skb() es llamado mientras se mantiene el bloqueo\n3. El asignador de memoria falla y llama a slab_out_of_memory()\n4. Esto desencadena printk() para la advertencia de OOM\n5. La ruta de salida de la consola llama a netpoll_send_udp()\n6. netpoll_send_udp() intenta adquirir el mismo skb_pool -\u003e lock\n7. Interbloqueo: el bloqueo ya est\u00e1 en posesi\u00f3n de la misma CPU\n\nPila de llamadas:\n  refill_skbs()\n    spin_lock_irqsave(\u0026skb_pool -\u003e lock)     \u003c-  bloqueo adquirido\n    __alloc_skb()\n      kmem_cache_alloc_node_noprof()\n        slab_out_of_memory()\n          printk()\n            console_flush_all()\n              netpoll_send_udp()\n                skb_dequeue()\n                  spin_lock_irqsave(\u0026skb_pool -\u003e lock)      \u003c-  intento de interbloqueo\n\nEste error fue expuesto por el commit 248f6571fd4c51 (\u0027netpoll: Optimize skb refilling on critical path\u0027) que elimin\u00f3 refill_skbs() de la ruta cr\u00edtica (donde el printk anidado estaba siendo diferido), permitiendo que el printk anidado fuera llamado desde dentro de refill_skbs()\n\nRefactorizar refill_skbs() para nunca asignar memoria mientras se mantiene el spinlock.\n\nOtra posible soluci\u00f3n para corregir este problema es proteger refill_skbs() de printks anidados, b\u00e1sicamente llamando a printk_deferred_{enter,exit}() en refill_skbs(), entonces, cualquier pr_warn() anidado ser\u00eda diferido.\n\nPrefiero este enfoque, dado que _creo_ que podr\u00eda ser una buena idea mover alloc_skb() de GFP_ATOMIC a GFP_KERNEL en el futuro, por lo tanto, tener alloc_skb() fuera del bloqueo ser\u00e1 un paso necesario.\n\nExiste un posible problema TOCTOU al verificar la longitud del pool y encolar el nuevo skb asignado, pero esto no es un problema, dado que un SKB extra en el pool es inofensivo y eventualmente ser\u00e1 utilizado."
          }
        ],
        "id": "CVE-2025-68169",
        "lastModified": "2026-10-14T13:10:00.187",
        "metrics": {},
        "published": "2025-12-16T14:15:48.760",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/06742a3ab884d7428c9050b205ffcf6a8a548397"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/327c20c21d80e0d87834b392d83ae73c955ad8ff"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Deferred"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-30T01:38:44+00:00",
      "cve": "CVE-2025-68169",
      "id": "CVE-2025-68169",
      "initial_release_date": "2025-12-16T00:00:00+00:00",
      "product_status:known_affected": "14",
      "product_status:known_not_affected": "260",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: Linux kernel: Denial of Service via deadlock in netpoll memory allocation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-68169.json",
      "version": "3"
    }
  }
}



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