CVE-2025-38217 (GCVE-0-2025-38217)
Vulnerability from cvelistv5 – Published: 2025-07-04 13:37 – Updated: 2026-05-11 21:23
VLAI
EPSS
VEX
Title
hwmon: (ftsteutates) Fix TOCTOU race in fts_read()
Summary
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (ftsteutates) Fix TOCTOU race in fts_read()
In the fts_read() function, when handling hwmon_pwm_auto_channels_temp,
the code accesses the shared variable data->fan_source[channel] twice
without holding any locks. It is first checked against
FTS_FAN_SOURCE_INVALID, and if the check passes, it is read again
when used as an argument to the BIT() macro.
This creates a Time-of-Check to Time-of-Use (TOCTOU) race condition.
Another thread executing fts_update_device() can modify the value of
data->fan_source[channel] between the check and its use. If the value
is changed to FTS_FAN_SOURCE_INVALID (0xff) during this window, the
BIT() macro will be called with a large shift value (BIT(255)).
A bit shift by a value greater than or equal to the type width is
undefined behavior and can lead to a crash or incorrect values being
returned to userspace.
Fix this by reading data->fan_source[channel] into a local variable
once, eliminating the race condition. Additionally, add a bounds check
to ensure the value is less than BITS_PER_LONG before passing it to
the BIT() macro, making the code more robust against undefined behavior.
This possible bug was found by an experimental static analysis tool
developed by our team.
Severity
4.7 (Medium)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
1c5759d8ce054961b454af69568a41e7e3210ee1 , < d95d87841d2a575bed3691884e8fedef57d7710d
(git)
Affected: 1c5759d8ce054961b454af69568a41e7e3210ee1 , < 83e2ba8971ccd8fc08319fc7593288f070d80a76 (git) Affected: 1c5759d8ce054961b454af69568a41e7e3210ee1 , < 4d646f627d3b7ed1cacca66e598af8bcd632d465 (git) Affected: 1c5759d8ce054961b454af69568a41e7e3210ee1 , < 14c9ede9ca4cd078ad76a6ab9617b81074eb58bf (git) |
guessed | |
| Linux | Linux |
Affected:
6.3
Unaffected: 0 , < 6.3 (semver) Unaffected: 6.6.95 , ≤ 6.6.* (semver) Unaffected: 6.12.35 , ≤ 6.12.* (semver) Unaffected: 6.15.4 , ≤ 6.15.* (semver) Unaffected: 6.16 , ≤ * (original_commit_for_fix) |
guessed |
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nhwmon: (ftsteutates) Fix TOCTOU race in fts_read()\n\nIn the fts_read() function, when handling hwmon_pwm_auto_channels_temp,\nthe code accesses the shared variable data-\u003efan_source[channel] twice\nwithout holding any locks. It is first checked against\nFTS_FAN_SOURCE_INVALID, and if the check passes, it is read again\nwhen used as an argument to the BIT() macro.\n\nThis creates a Time-of-Check to Time-of-Use (TOCTOU) race condition.\nAnother thread executing fts_update_device() can modify the value of\ndata-\u003efan_source[channel] between the check and its use. If the value\nis changed to FTS_FAN_SOURCE_INVALID (0xff) during this window, the\nBIT() macro will be called with a large shift value (BIT(255)).\nA bit shift by a value greater than or equal to the type width is\nundefined behavior and can lead to a crash or incorrect values being\nreturned to userspace.\n\nFix this by reading data-\u003efan_source[channel] into a local variable\nonce, eliminating the race condition. Additionally, add a bounds check\nto ensure the value is less than BITS_PER_LONG before passing it to\nthe BIT() macro, making the code more robust against undefined behavior.\n\nThis possible bug was found by an experimental static analysis tool\ndeveloped by our team."
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"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: hwmon: (ftsteutates) Corregir la ejecuci\u00f3n TOCTOU en fts_read() En la funci\u00f3n fts_read(), al manejar hwmon_pwm_auto_channels_temp, el c\u00f3digo accede a la variable compartida data-\u0026gt;fan_source[channel] dos veces sin mantener ning\u00fan bloqueo. Primero se compara con FTS_FAN_SOURCE_INVALID y, si la comprobaci\u00f3n es correcta, se vuelve a leer cuando se usa como argumento de la macro BIT(). Esto crea una condici\u00f3n de ejecuci\u00f3n de tiempo de comprobaci\u00f3n a tiempo de uso (TOCTOU). Otro hilo que ejecute fts_update_device() puede modificar el valor de data-\u0026gt;fan_source[channel] entre la comprobaci\u00f3n y su uso. Si el valor se cambia a FTS_FAN_SOURCE_INVALID (0xff) durante esta ventana, se llamar\u00e1 a la macro BIT() con un valor de desplazamiento grande (BIT(255)). Un desplazamiento de bits por un valor mayor o igual al ancho del tipo es un comportamiento indefinido que puede provocar un fallo o la devoluci\u00f3n de valores incorrectos al espacio de usuario. Para solucionarlo, lea data-\u0026gt;fan_source[channel] en una variable local una vez, eliminando as\u00ed la condici\u00f3n de ejecuci\u00f3n. Adem\u00e1s, a\u00f1ada una comprobaci\u00f3n de los l\u00edmites para garantizar que el valor sea menor que BITS_PER_LONG antes de pasarlo a la macro BIT(), lo que aumenta la robustez del c\u00f3digo frente a comportamientos indefinidos. Este posible error fue detectado por una herramienta de an\u00e1lisis est\u00e1tico experimental desarrollada por nuestro equipo."
}
],
"id": "CVE-2025-38217",
"lastModified": "2026-06-17T09:16:24.533",
"metrics": {
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{
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"attackComplexity": "HIGH",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 4.7,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
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"source": "nvd@nist.gov",
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"published": "2025-07-04T14:15:30.227",
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"value": "CWE-367"
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"redhat_vex": {
"aggregate_severity": "None",
"current_release_date": "2026-11-06T14:59:46+00:00",
"cve": "CVE-2025-38217",
"id": "CVE-2025-38217",
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"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: hwmon: (ftsteutates) Fix TOCTOU race in fts_read()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-38217.json",
"version": "3"
}
}
}
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