FKIE_CVE-2025-40142

Vulnerability from fkie_nvd - Published: 2025-11-12 11:15 - Updated: 2026-10-19 21:10
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: ALSA: pcm: Disable bottom softirqs as part of spin_lock_irq() on PREEMPT_RT snd_pcm_group_lock_irq() acquires a spinlock_t and disables interrupts via spin_lock_irq(). This also implicitly disables the handling of softirqs such as TIMER_SOFTIRQ. On PREEMPT_RT softirqs are preemptible and spin_lock_irq() does not disable them. That means a timer can be invoked during spin_lock_irq() on the same CPU. Due to synchronisations reasons local_bh_disable() has a per-CPU lock named softirq_ctrl.lock which synchronizes individual softirq against each other. syz-bot managed to trigger a lockdep report where softirq_ctrl.lock is acquired in hrtimer_cancel() in addition to hrtimer_run_softirq(). This is a possible deadlock. The softirq_ctrl.lock can not be made part of spin_lock_irq() as this would lead to too much synchronisation against individual threads on the system. To avoid the possible deadlock, softirqs must be manually disabled before the lock is acquired. Disable softirqs before the lock is acquired on PREEMPT_RT.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3969b6193cb7a45aa5fb4ec68f215e9e7f93d39a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/63ee96c7f47df239ee0a6e8108b6bfd8c98334ae
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9fc4a3da9a0259a0500848b5d8657918efde176b
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "sound/core/pcm_native.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "63ee96c7f47df239ee0a6e8108b6bfd8c98334ae",
              "status": "affected",
              "version": "d2d6422f8bd17c6bb205133e290625a564194496",
              "versionType": "git"
            },
            {
              "lessThan": "3969b6193cb7a45aa5fb4ec68f215e9e7f93d39a",
              "status": "affected",
              "version": "d2d6422f8bd17c6bb205133e290625a564194496",
              "versionType": "git"
            },
            {
              "lessThan": "9fc4a3da9a0259a0500848b5d8657918efde176b",
              "status": "affected",
              "version": "d2d6422f8bd17c6bb205133e290625a564194496",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "sound/core/pcm_native.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.12"
            },
            {
              "lessThan": "6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: Disable bottom softirqs as part of spin_lock_irq() on PREEMPT_RT\n\nsnd_pcm_group_lock_irq() acquires a spinlock_t and disables interrupts\nvia spin_lock_irq(). This also implicitly disables the handling of\nsoftirqs such as TIMER_SOFTIRQ.\nOn PREEMPT_RT softirqs are preemptible and spin_lock_irq() does not\ndisable them. That means a timer can be invoked during spin_lock_irq()\non the same CPU. Due to synchronisations reasons local_bh_disable() has\na per-CPU lock named softirq_ctrl.lock which synchronizes individual\nsoftirq against each other.\nsyz-bot managed to trigger a lockdep report where softirq_ctrl.lock is\nacquired in hrtimer_cancel() in addition to hrtimer_run_softirq(). This\nis a possible deadlock.\n\nThe softirq_ctrl.lock can not be made part of spin_lock_irq() as this\nwould lead to too much synchronisation against individual threads on the\nsystem. To avoid the possible deadlock, softirqs must be manually\ndisabled before the lock is acquired.\n\nDisable softirqs before the lock is acquired on PREEMPT_RT."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nALSA: pcm: Deshabilitar softirqs inferiores como parte de spin_lock_irq() en PREEMPT_RT\n\nsnd_pcm_group_lock_irq() adquiere un spinlock_t y deshabilita las interrupciones a trav\u00e9s de spin_lock_irq(). Esto tambi\u00e9n deshabilita impl\u00edcitamente el manejo de softirqs como TIMER_SOFTIRQ.\nEn PREEMPT_RT, los softirqs son preemptibles y spin_lock_irq() no los deshabilita. Eso significa que se puede invocar un temporizador durante spin_lock_irq() en la misma CPU. Debido a razones de sincronizaci\u00f3n, local_bh_disable() tiene un bloqueo por CPU llamado softirq_ctrl.lock que sincroniza los softirqs individuales entre s\u00ed.\nsyz-bot logr\u00f3 activar un informe de lockdep donde softirq_ctrl.lock se adquiere en hrtimer_cancel() adem\u00e1s de hrtimer_run_softirq(). Esto es un posible interbloqueo.\n\nEl softirq_ctrl.lock no puede formar parte de spin_lock_irq(), ya que esto llevar\u00eda a demasiada sincronizaci\u00f3n contra hilos individuales en el sistema. Para evitar el posible interbloqueo, los softirqs deben deshabilitarse manualmente antes de que se adquiera el bloqueo.\n\nDeshabilitar los softirqs antes de que se adquiera el bloqueo en PREEMPT_RT."
    }
  ],
  "id": "CVE-2025-40142",
  "lastModified": "2026-10-19T21:10:00.160",
  "metrics": {},
  "published": "2025-11-12T11:15:44.017",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3969b6193cb7a45aa5fb4ec68f215e9e7f93d39a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/63ee96c7f47df239ee0a6e8108b6bfd8c98334ae"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9fc4a3da9a0259a0500848b5d8657918efde176b"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Deferred"
}



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