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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/fpu: Drop fpregs lock before inheriting FPU permissions\n\nMike Galbraith reported the following against an old fork of preempt-rt\nbut the same issue also applies to the current preempt-rt tree.\n\n   BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46\n   in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: systemd\n   preempt_count: 1, expected: 0\n   RCU nest depth: 0, expected: 0\n   Preemption disabled at:\n   fpu_clone\n   CPU: 6 PID: 1 Comm: systemd Tainted: G            E       (unreleased)\n   Call Trace:\n    \u003cTASK\u003e\n    dump_stack_lvl\n    ? fpu_clone\n    __might_resched\n    rt_spin_lock\n    fpu_clone\n    ? copy_thread\n    ? copy_process\n    ? shmem_alloc_inode\n    ? kmem_cache_alloc\n    ? kernel_clone\n    ? __do_sys_clone\n    ? do_syscall_64\n    ? __x64_sys_rt_sigprocmask\n    ? syscall_exit_to_user_mode\n    ? do_syscall_64\n    ? syscall_exit_to_user_mode\n    ? do_syscall_64\n    ? syscall_exit_to_user_mode\n    ? do_syscall_64\n    ? exc_page_fault\n    ? entry_SYSCALL_64_after_hwframe\n    \u003c/TASK\u003e\n\nMike says:\n\n  The splat comes from fpu_inherit_perms() being called under fpregs_lock(),\n  and us reaching the spin_lock_irq() therein due to fpu_state_size_dynamic()\n  returning true despite static key __fpu_state_size_dynamic having never\n  been enabled.\n\nMike\u0027s assessment looks correct. fpregs_lock on a PREEMPT_RT kernel disables\npreemption so calling spin_lock_irq() in fpu_inherit_perms() is unsafe. This\nproblem exists since commit\n\n  9e798e9aa14c (\"x86/fpu: Prepare fpu_clone() for dynamically enabled features\").\n\nEven though the original bug report should not have enabled the paths at\nall, the bug still exists.\n\nfpregs_lock is necessary when editing the FPU registers or a task\u0027s FP\nstate but it is not necessary for fpu_inherit_perms(). The only write\nof any FP state in fpu_inherit_perms() is for the new child which is\nnot running yet and cannot context switch or be borrowed by a kernel\nthread yet. Hence, fpregs_lock is not protecting anything in the new\nchild until clone() completes and can be dropped earlier. The siglock\nstill needs to be acquired by fpu_inherit_perms() as the read of the\nparent\u0027s permissions has to be serialised.\n\n  [ bp: Cleanup splat. ]"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: x86/fpu: Eliminar el bloqueo de fpregs antes de heredar los permisos de FPU Mike Galbraith inform\u00f3 lo siguiente contra una antigua bifurcaci\u00f3n de preempt-rt, pero el mismo problema tambi\u00e9n se aplica al \u00e1rbol preempt-rt actual. ERROR: funci\u00f3n inactiva llamada desde un contexto no v\u00e1lido en kernel/locking/spinlock_rt.c:46 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: systemd preempt_count: 1, expected: 0 Profundidad de anidamiento de RCU: 0, expected: 0 Preempci\u00f3n deshabilitada en: fpu_clone CPU: 6 PID: 1 Comm: systemd Tainted: GE (no publicado) Rastreo de llamadas:   dump_stack_lvl ? fpu_clone __might_resched rt_spin_lock fpu_clone ? copy_thread ? copy_process ? shmem_alloc_inode ? kmem_cache_alloc ? kernel_clone ? __do_sys_clone ? do_syscall_64 ? __x64_sys_rt_sigprocmask ? syscall_exit_to_user_mode ? do_syscall_64 ? syscall_exit_to_user_mode ? do_syscall_64 ? syscall_exit_to_user_mode ? do_syscall_64 ? exc_page_fault ? entry_SYSCALL_64_after_hwframe   Mike dice: El problema se debe a que fpu_inherit_perms() se llama bajo fpregs_lock() y a que alcanzamos spin_lock_irq() debido a que fpu_state_size_dynamic() devuelve verdadero a pesar de que la clave est\u00e1tica __fpu_state_size_dynamic nunca se ha habilitado. La evaluaci\u00f3n de Mike parece correcta. fpregs_lock en un kernel PREEMPT_RT deshabilita la preempci\u00f3n, por lo que llamar a spin_lock_irq() en fpu_inherit_perms() no es seguro. Este problema existe desde la confirmaci\u00f3n 9e798e9aa14c (\"x86/fpu: Preparar fpu_clone() para funciones habilitadas din\u00e1micamente\"). Aunque el informe de error original no deber\u00eda haber habilitado las rutas, el error persiste. fpregs_lock es necesario al editar los registros de FPU o el estado de FP de una tarea, pero no es necesario para fpu_inherit_perms(). La \u00fanica escritura de cualquier estado de FP en fpu_inherit_perms() es para el nuevo hijo, que a\u00fan no se est\u00e1 ejecutando y a\u00fan no puede cambiar de contexto ni ser tomado prestado por un hilo del kernel. Por lo tanto, fpregs_lock no protege nada en el nuevo hijo hasta que clone() se complete y pueda eliminarse antes. El siglock a\u00fan debe ser adquirido por fpu_inherit_perms(), ya que la lectura de los permisos del padre debe serializarse. [bp: Limpieza splat.]"
    }
  ],
  "id": "CVE-2022-49783",
  "lastModified": "2025-11-07T17:48:52.480",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2025-05-01T15:16:01.510",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
        "Patch"
      ],
      "url": "https://git.kernel.org/stable/c/36b038791e1e2baea892e9276588815fd14894b4"
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    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
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          "lang": "en",
          "value": "NVD-CWE-noinfo"
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      "source": "nvd@nist.gov",
      "type": "Primary"
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}