CVE-2024-50226
Estado: ModificadaAlta (7.8)—
In the Linux kernel, the following vulnerability has been resolved:
cxl/port: Fix use-after-free, permit out-of-order decoder shutdown
In support of investigating an initialization failure report [1], cxl_test was updated to register mock memory-devices after the mock root-port/bus device had been registered. That led to cxl_test crashing with a use-after-free bug with the following signature:
At 1) a region has been established with 2 endpoint decoders (7.0 and 14.0). Those endpoints share a common switch-decoder in the topology (3.0).
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At teardown, 2), decoder14.0 is the first to be removed and hits the "out of order reset case" in the switch decoder. The effect though is that region3 cleanup is aborted leaving it in-tact and referencing decoder14.0. At 3) the second attempt to teardown region3 trips over the stale decoder14.0 object which has long since been deleted.
The fix here is to recognize that the CXL specification places no mandate on in-order shutdown of switch-decoders, the driver enforces in-order allocation, and hardware enforces in-order commit. So, rather than fail and leave objects dangling, always remove them.
In support of making cxl_region_decode_reset() always succeed, cxl_region_invalidate_memregion() failures are turned into warnings. Crashing the kernel is ok there since system integrity is at risk if caches cannot be managed around physical address mutation events like CXL region destruction.
A new device_for_each_child_reverse_from() is added to cleanup port->commit_end after all dependent decoders have been disabled. In other words if decoders are allocated 0->1->2 and disabled 1->2->0 then port->commit_end only decrements from 2 after 2 has been disabled, and it decrements all the way to zero since 1 was disabled previously.
Detalles técnicos trazas, registros y código del informe original
cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem0:decoder7.0 @ 0 next: cxl_switch_uport.0 nr_eps: 1 nr_targets: 1
cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem4:decoder14.0 @ 1 next: cxl_switch_uport.0 nr_eps: 2 nr_targets: 1
cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[0] = cxl_switch_dport.0 for mem0:decoder7.0 @ 0
1) cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[1] = cxl_switch_dport.4 for mem4:decoder14.0 @ 1
[..]
cxld_unregister: cxl decoder14.0:
cxl_region_decode_reset: cxl_region region3:
mock_decoder_reset: cxl_port port3: decoder3.0 reset
2) mock_decoder_reset: cxl_port port3: decoder3.0: out of order reset, expected decoder3.1
cxl_endpoint_decoder_release: cxl decoder14.0:
[..]
cxld_unregister: cxl decoder7.0:
3) cxl_region_decode_reset: cxl_region region3:
Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6bc3: 0000 [#1] PREEMPT SMP PTI
[..]
RIP: 0010:to_cxl_port+0x8/0x60 [cxl_core]
[..]
Call Trace:
<TASK>
cxl_region_decode_reset+0x69/0x190 [cxl_core]
cxl_region_detach+0xe8/0x210 [cxl_core]
cxl_decoder_kill_region+0x27/0x40 [cxl_core]
cxld_unregister+0x5d/0x60 [cxl_core]CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.24%
- Percentil entre todas las CVEs puntuadas: 14
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1068Exploitation for Privilege Escalationprivilege escalation75 % - Impacto principal
T1059Command and Scripting Interpreterexecution60 %
Vulnerabilidad CWE-416 (use-after-free) en el kernel de Linux con AV:L/PR:L/UI:N permite escalada de privilegios (I:H) mediante acceso local. Puede permitir ejecución de código tras corrupción de memoria.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
CWE
- CWE-416
- CWE-416
Referencias
JSON original (NVD)
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncxl/port: Fix use-after-free, permit out-of-order decoder shutdown\n\nIn support of investigating an initialization failure report [1],\ncxl_test was updated to register mock memory-devices after the mock\nroot-port/bus device had been registered. That led to cxl_test crashing\nwith a use-after-free bug with the following signature:\n\n cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem0:decoder7.0 @ 0 next: cxl_switch_uport.0 nr_eps: 1 nr_targets: 1\n cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem4:decoder14.0 @ 1 next: cxl_switch_uport.0 nr_eps: 2 nr_targets: 1\n cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[0] = cxl_switch_dport.0 for mem0:decoder7.0 @ 0\n1) cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[1] = cxl_switch_dport.4 for mem4:decoder14.0 @ 1\n [..]\n cxld_unregister: cxl decoder14.0:\n cxl_region_decode_reset: cxl_region region3:\n mock_decoder_reset: cxl_port port3: decoder3.0 reset\n2) mock_decoder_reset: cxl_port port3: decoder3.0: out of order reset, expected decoder3.1\n cxl_endpoint_decoder_release: cxl decoder14.0:\n [..]\n cxld_unregister: cxl decoder7.0:\n3) cxl_region_decode_reset: cxl_region region3:\n Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6bc3: 0000 [#1] PREEMPT SMP PTI\n [..]\n RIP: 0010:to_cxl_port+0x8/0x60 [cxl_core]\n [..]\n Call Trace:\n <TASK>\n cxl_region_decode_reset+0x69/0x190 [cxl_core]\n cxl_region_detach+0xe8/0x210 [cxl_core]\n cxl_decoder_kill_region+0x27/0x40 [cxl_core]\n cxld_unregister+0x5d/0x60 [cxl_core]\n\nAt 1) a region has been established with 2 endpoint decoders (7.0 and\n14.0). Those endpoints share a common switch-decoder in the topology\n(3.0). At teardown, 2), decoder14.0 is the first to be removed and hits\nthe \"out of order reset case\" in the switch decoder. The effect though\nis that region3 cleanup is aborted leaving it in-tact and\nreferencing decoder14.0. At 3) the second attempt to teardown region3\ntrips over the stale decoder14.0 object which has long since been\ndeleted.\n\nThe fix here is to recognize that the CXL specification places no\nmandate on in-order shutdown of switch-decoders, the driver enforces\nin-order allocation, and hardware enforces in-order commit. So, rather\nthan fail and leave objects dangling, always remove them.\n\nIn support of making cxl_region_decode_reset() always succeed,\ncxl_region_invalidate_memregion() failures are turned into warnings.\nCrashing the kernel is ok there since system integrity is at risk if\ncaches cannot be managed around physical address mutation events like\nCXL region destruction.\n\nA new device_for_each_child_reverse_from() is added to cleanup\nport->commit_end after all dependent decoders have been disabled. In\nother words if decoders are allocated 0->1->2 and disabled 1->2->0 then\nport->commit_end only decrements from 2 after 2 has been disabled, and\nit decrements all the way to zero since 1 was disabled previously."
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"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: cxl/port: Corregir use-after-free, permitir el apagado del decodificador fuera de orden. En apoyo a la investigación de un informe de falla de inicialización [1], cxl_test se actualizó para registrar dispositivos de memoria simulados después de que se hubiera registrado el dispositivo de puerto raíz/bus simulado. Esto provocó que cxl_test se bloqueara con un error de use-after-free con la siguiente firma: cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem0:decoder7.0 @ 0 next: cxl_switch_uport.0 nr_eps: 1 nr_targets: 1 cxl_port_attach_region: cxl region3: cxl_host_bridge.0:port3 decoder3.0 add: mem4:decoder14.0 @ 1 next: cxl_switch_uport.0 nr_eps: 2 nr_targets: 1 cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[0] = cxl_switch_dport.0 for mem0:decoder7.0 @ 0 1) cxl_port_setup_targets: cxl region3: cxl_switch_uport.0:port6 target[1] = cxl_switch_dport.4 para mem4:decoder14.0 @ 1 [..] cxld_unregister: cxl decoder14.0: cxl_region_decode_reset: cxl_region region3: mock_decoder_reset: cxl_port port3: decoder3.0 restablecer 2) mock_decoder_reset: cxl_port port3: decoder3.0: restablecimiento fuera de servicio, se esperaba decoder3.1 cxl_endpoint_decoder_release: cxl decoder14.0: [..] cxld_unregister: cxl decoder7.0: 3) cxl_region_decode_reset: cxl_region region3: Vaya: error de protección general, probablemente para dirección no canónica 0x6b6b6b6b6b6b6bc3: 0000 [#1] PREEMPT SMP PTI [..] RIP: 0010:to_cxl_port+0x8/0x60 [cxl_core] [..] Rastreo de llamada: cxl_region_decode_reset+0x69/0x190 [cxl_core] cxl_region_detach+0xe8/0x210 [cxl_core] cxl_decoder_kill_region+0x27/0x40 [cxl_core] cxld_unregister+0x5d/0x60 [cxl_core] En 1) se ha establecido una región con 2 decodificadores de endpoint (7.0 y 14.0). Esos endpoints comparten un decodificador de conmutación común en la topología (3.0). En el desmontaje, 2), decoder14.0 es el primero en ser eliminado y llega al \"caso de reinicio fuera de orden\" en el decodificador de conmutación. El efecto, sin embargo, es que la limpieza de la región 3 se aborta dejándola intacta y haciendo referencia a decoder14.0. En 3), el segundo intento de desmontaje de la región 3 tropieza con el objeto decoder14.0 obsoleto que ha sido eliminado hace mucho tiempo. La solución aquí es reconocer que la especificación CXL no impone ningún mandato sobre el apagado en orden de los decodificadores de conmutación, el controlador impone la asignación en orden y el hardware impone el commit en orden. Por lo tanto, en lugar de fallar y dejar objetos colgando, siempre elimínelos. Para respaldar que cxl_region_decode_reset() siempre tenga éxito, los fallos de cxl_region_invalidate_memregion() se convierten en advertencias. Allí está bien hacer que el núcleo se bloquee, ya que la integridad del sistema está en riesgo si las cachés no se pueden administrar en torno a eventos de mutación de direcciones físicas como la destrucción de la región CXL. Se agrega un nuevo device_for_each_child_reverse_from() para limpiar port->commit_end después de que se hayan deshabilitado todos los decodificadores dependientes. En otras palabras, si se asignan decodificadores 0->1->2 y se deshabilitan 1->2->0, entonces port->commit_end solo disminuye desde 2 después de que se haya deshabilitado 2, y disminuye hasta cero ya que 1 se deshabilitó previamente."
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],
"lastModified": "2026-06-17T08:03:55.200",
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