FKIE_CVE-2026-74653

Vulnerability from fkie_nvd - Published: 2026-08-22 16:16 - Updated: 2026-10-14 13:10
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: serial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx The NXP LPC32xx UART (PORT_LPC3220) can latch an RX character-timeout interrupt while the RX FIFO is empty: IIR reports UART_IIR_RX_TIMEOUT (0x0c) but LSR.DR is clear. A character timeout is only cleared by reading RHR, but serial8250_rx_chars() reads RHR only when LSR.DR is set, so nothing ever clears the condition. The interrupt is level-triggered and re-fires immediately, so on a single-core ARM926 the resulting interrupt storm livelocks the CPU. It is reproducible when userspace repeatedly opens the front-panel port (ttyS1): serial8250_do_set_termios() re-enables interrupts on unlock and the handler then spins forever with iir=0xcc lsr=0x60 ier=0x05, tripping the soft-lockup detector in serial8250_handle_irq_locked(). LPC32xx has no dedicated 8250 glue driver, it's driven by the generic 8250_of. Add a hardware specific handle_irq for PORT_LPC3220, wired up in of_platform_serial_setup() the same way fsl8250_handle_irq is installed. The handler follows dw8250_handle_irq(): on an RX timeout with an empty FIFO (LSR.DR and LSR.BI clear) it does one throwaway RHR read to clear the condition, then calls serial8250_handle_irq_locked(). No real received data is ever discarded, and it is a no-op on healthy UARTs which never report a timeout with DR clear. This is the same class of bug already worked around in other 8250 drivers; see commit 424d79183af0 ("serial: 8250_dw: Avoid "too much work" from bogus rx timeout interrupt") which reports the identical iir=0xcc/lsr=0x60. See also UART_RX_TIMEOUT_QUIRK in 8250_omap, and the note in 8250_bcm7271.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/1423415471274abda87024967d7fe2206ceee0ea
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3ce24bc4d115336218e59b7e286fd3a79f4fc4c6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7795e8abedc86438cae0454602cbf9038b94bf38
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c321dc5172c8c66e21ffbeeb7a2ebb88ae6fd4c3
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/tty/serial/8250/8250_of.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "c321dc5172c8c66e21ffbeeb7a2ebb88ae6fd4c3",
              "status": "affected",
              "version": "e6e912c4964ce5976e508881207dfa96d5f856d7",
              "versionType": "git"
            },
            {
              "lessThan": "3ce24bc4d115336218e59b7e286fd3a79f4fc4c6",
              "status": "affected",
              "version": "e6e912c4964ce5976e508881207dfa96d5f856d7",
              "versionType": "git"
            },
            {
              "lessThan": "7795e8abedc86438cae0454602cbf9038b94bf38",
              "status": "affected",
              "version": "e6e912c4964ce5976e508881207dfa96d5f856d7",
              "versionType": "git"
            },
            {
              "lessThan": "1423415471274abda87024967d7fe2206ceee0ea",
              "status": "affected",
              "version": "e6e912c4964ce5976e508881207dfa96d5f856d7",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/tty/serial/8250/8250_of.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.36"
            },
            {
              "lessThan": "2.6.36",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.106",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "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\nserial: 8250_of: clear stuck empty-FIFO RX-timeout on LPC32xx\n\nThe NXP LPC32xx UART (PORT_LPC3220) can latch an RX character-timeout\ninterrupt while the RX FIFO is empty: IIR reports UART_IIR_RX_TIMEOUT\n(0x0c) but LSR.DR is clear. A character timeout is only cleared by\nreading RHR, but serial8250_rx_chars() reads RHR only when LSR.DR is\nset, so nothing ever clears the condition. The interrupt is\nlevel-triggered and re-fires immediately, so on a single-core ARM926\nthe resulting interrupt storm livelocks the CPU.\n\nIt is reproducible when userspace repeatedly opens the front-panel port\n(ttyS1): serial8250_do_set_termios() re-enables interrupts on unlock and\nthe handler then spins forever with iir=0xcc lsr=0x60 ier=0x05, tripping\nthe soft-lockup detector in serial8250_handle_irq_locked().\n\nLPC32xx has no dedicated 8250 glue driver, it\u0027s driven by the generic\n8250_of. Add a hardware specific handle_irq for PORT_LPC3220, wired up\nin of_platform_serial_setup() the same way fsl8250_handle_irq is\ninstalled. The handler follows dw8250_handle_irq(): on an RX timeout\nwith an empty FIFO (LSR.DR and LSR.BI clear) it does one throwaway RHR\nread to clear the condition, then calls serial8250_handle_irq_locked().\nNo real received data is ever discarded, and it is a no-op on healthy\nUARTs which never report a timeout with DR clear.\n\nThis is the same class of bug already worked around in other 8250 drivers;\nsee commit 424d79183af0 (\"serial: 8250_dw: Avoid \"too much work\" from bogus rx timeout interrupt\")\nwhich reports the identical iir=0xcc/lsr=0x60. See also\nUART_RX_TIMEOUT_QUIRK in 8250_omap, and the note in 8250_bcm7271."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nserial: 8250_of: limpiar el tiempo de espera de RX atascado de FIFO vac\u00edo en LPC32xx\n\nLa UART NXP LPC32xx (PORT_LPC3220) puede enganchar una interrupci\u00f3n de tiempo de espera de car\u00e1cter RX mientras la FIFO de RX est\u00e1 vac\u00eda: IIR informa UART_IIR_RX_TIMEOUT (0x0c) pero LSR.DR est\u00e1 despejado. Un tiempo de espera de car\u00e1cter solo se borra leyendo RHR, pero serial8250_rx_chars() lee RHR solo cuando LSR.DR est\u00e1 establecido, por lo que nada borra nunca la condici\u00f3n. La interrupci\u00f3n es activada por nivel y se vuelve a disparar inmediatamente, por lo que en un ARM926 de un solo n\u00facleo la tormenta de interrupciones resultante bloquea la CPU.\n\nEs reproducible cuando el espacio de usuario abre repetidamente el puerto del panel frontal (ttyS1): serial8250_do_set_termios() vuelve a habilitar las interrupciones al desbloquear y el gestor luego gira indefinidamente con iir=0xcc lsr=0x60 ier=0x05, activando el detector de bloqueo suave en serial8250_handle_irq_locked().\n\nLPC32xx no tiene un controlador de pegamento 8250 dedicado, es impulsado por el gen\u00e9rico 8250_of. A\u00f1adir un handle_irq espec\u00edfico del hardware para PORT_LPC3220, cableado en of_platform_serial_setup() de la misma manera que se instala fsl8250_handle_irq. El gestor sigue a dw8250_handle_irq(): en un tiempo de espera de RX con una FIFO vac\u00eda (LSR.DR y LSR.BI despejados) realiza una lectura de RHR de descarte para borrar la condici\u00f3n, luego llama a serial8250_handle_irq_locked(). Nunca se descartan datos reales recibidos, y es una operaci\u00f3n nula en UARTs saludables que nunca informan un tiempo de espera con DR despejado.\n\nEsta es la misma clase de error ya solucionado en otros controladores 8250; ver commit 424d79183af0 (\u0027serial: 8250_dw: Evitar \u0027demasiado trabajo\u0027 de interrupci\u00f3n de tiempo de espera de rx falsa\u0027) que informa el id\u00e9ntico iir=0xcc/lsr=0x60. Ver tambi\u00e9n UART_RX_TIMEOUT_QUIRK en 8250_omap, y la nota en 8250_bcm7271."
    }
  ],
  "id": "CVE-2026-74653",
  "lastModified": "2026-10-14T13:10:00.187",
  "metrics": {},
  "published": "2026-08-22T16:16:38.827",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/1423415471274abda87024967d7fe2206ceee0ea"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3ce24bc4d115336218e59b7e286fd3a79f4fc4c6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7795e8abedc86438cae0454602cbf9038b94bf38"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c321dc5172c8c66e21ffbeeb7a2ebb88ae6fd4c3"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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