CVE-2026-23168

Estado: AnalizadaMedia (5.5)—

In the Linux kernel, the following vulnerability has been resolved:

flex_proportions: make fprop_new_period() hardirq safe

Bernd has reported a lockdep splat from flexible proportions code that is essentially complaining about the following race:

<hardirq is raised> ... blk_mq_end_request() blk_update_request() ext4_end_bio() folio_end_writeback() __wb_writeout_add() __fprop_add_percpu_max() if (unlikely(max_frac < FPROP_FRAC_BASE)) { fprop_fraction_percpu() seq = read_seqcount_begin(&p->sequence); - sees odd sequence so loops indefinitely

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Note that a deadlock like this is only possible if the bdi has configured maximum fraction of writeout throughput which is very rare in general but frequent for example for FUSE bdis. To fix this problem we have to make sure write section of the sequence counter is irqsafe.

Detalles técnicos trazas, registros y código del informe original

<timer fires>
run_timer_softirq - we are in softirq context
  call_timer_fn
    writeout_period
      fprop_new_period
        write_seqcount_begin(&p->sequence);

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Puntuación base: 5.5

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.12%
Percentil entre todas las CVEs puntuadas: 2
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).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

NVD-CWE-noinfo

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nflex_proportions: make fprop_new_period() hardirq safe\n\nBernd has reported a lockdep splat from flexible proportions code that is\nessentially complaining about the following race:\n\n<timer fires>\nrun_timer_softirq - we are in softirq context\n  call_timer_fn\n    writeout_period\n      fprop_new_period\n        write_seqcount_begin(&p->sequence);\n\n        <hardirq is raised>\n        ...\n        blk_mq_end_request()\n\t  blk_update_request()\n\t    ext4_end_bio()\n\t      folio_end_writeback()\n\t\t__wb_writeout_add()\n\t\t  __fprop_add_percpu_max()\n\t\t    if (unlikely(max_frac < FPROP_FRAC_BASE)) {\n\t\t      fprop_fraction_percpu()\n\t\t\tseq = read_seqcount_begin(&p->sequence);\n\t\t\t  - sees odd sequence so loops indefinitely\n\nNote that a deadlock like this is only possible if the bdi has configured\nmaximum fraction of writeout throughput which is very rare in general but\nfrequent for example for FUSE bdis.  To fix this problem we have to make\nsure write section of the sequence counter is irqsafe."
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      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nflex_proportions: hacer que fprop_new_period() sea seguro para hardirq\n\nBernd ha reportado un lockdep splat del código de proporciones flexibles que esencialmente se queja de la siguiente condición de carrera:\n\n\nrun_timer_softirq - estamos en contexto de softirq\n  call_timer_fn\n    writeout_period\n      fprop_new_period\n        write_seqcount_begin(&amp;p-&gt;sequence);\n\n        \n        ...\n        blk_mq_end_request()\n\t  blk_update_request()\n\t    ext4_end_bio()\n\t      folio_end_writeback()\n\t\t__wb_writeout_add()\n\t\t  __fprop_add_percpu_max()\n\t\t    if (unlikely(max_frac &lt; FPROP_FRAC_BASE)) {\n\t\t      fprop_fraction_percpu()\n\t\t\tseq = read_seqcount_begin(&amp;p-&gt;sequence);\n\t\t\t  - ve una secuencia impar por lo que entra en un bucle indefinido\n\nTenga en cuenta que un interbloqueo como este solo es posible si el bdi ha configurado una fracción máxima de rendimiento de escritura, lo cual es muy raro en general pero frecuente, por ejemplo, para bdis FUSE. Para solucionar este problema, tenemos que asegurarnos de que la sección de escritura del contador de secuencia sea irqsafe."
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