CVE-2022-49783

{"id": "CVE-2022-49783", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.8}]}, "published": "2025-05-01T15:16:01.510", "references": [{"url": "https://git.kernel.org/stable/c/36b038791e1e2baea892e9276588815fd14894b4", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/c6e8a7a1780af3da65e78a615f7d0874da6aabb0", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "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 <TASK>\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 </TASK>\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's 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's 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's 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.]"}], "lastModified": "2025-11-07T17:48:52.480", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "64F9ADD1-3ADB-4D66-A00F-4A83010B05F0", "versionEndExcluding": "6.0.10", "versionStartIncluding": "5.16"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.1:rc1:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "E7E331DA-1FB0-4DEC-91AC-7DA69D461C11"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.1:rc2:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "17F0B248-42CF-4AE6-A469-BB1BAE7F4705"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.1:rc3:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "E2422816-0C14-4B5E-A1E6-A9D776E5C49B"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.1:rc4:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "1C6E00FE-5FB9-4D20-A1A1-5A32128F9B76"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.1:rc5:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "35B26BE4-43A6-4A36-A7F6-5B3F572D9186"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}