CVE-2022-49075
Estado: ModificadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix qgroup reserve overflow the qgroup limit
We use extent_changeset->bytes_changed in qgroup_reserve_data() to record how many bytes we set for EXTENT_QGROUP_RESERVED state. Currently the bytes_changed is set as "unsigned int", and it will overflow if we try to fallocate a range larger than 4GiB. The result is we reserve less bytes and eventually break the qgroup limit.
Unlike regular buffered/direct write, which we use one changeset for each ordered extent, which can never be larger than 256M. For fallocate, we use one changeset for the whole range, thus it no longer respects the 256M per extent limit, and caused the problem.
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The following example test script reproduces the problem:
When running the test:
Since we have no control of how bytes_changed is used, it's better to set it to u64.
Detalles técnicos trazas, registros y código del informe original
$ cat qgroup-overflow.sh #!/bin/bash DEV=/dev/sdj MNT=/mnt/sdj mkfs.btrfs -f $DEV mount $DEV $MNT # Set qgroup limit to 2GiB. btrfs quota enable $MNT btrfs qgroup limit 2G $MNT # Try to fallocate a 3GiB file. This should fail. echo echo "Try to fallocate a 3GiB file..." fallocate -l 3G $MNT/3G.file # Try to fallocate a 5GiB file. echo echo "Try to fallocate a 5GiB file..." fallocate -l 5G $MNT/5G.file # See we break the qgroup limit. echo sync btrfs qgroup show -r $MNT umount $MNT $ ./qgroup-overflow.sh (...) Try to fallocate a 3GiB file... fallocate: fallocate failed: Disk quota exceeded Try to fallocate a 5GiB file... qgroupid rfer excl max_rfer -------- ---- ---- -------- 0/5 5.00GiB 5.00GiB 2.00GiB
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: 0.67%
- Percentil entre todas las CVEs puntuadas: 50
- Fecha de la puntuación: 5/10/2026
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)
CWE
- CWE-190
Referencias
- https://git.kernel.org/stable/c/0355387ea5b02d353c9415613fab908fac5c52a6
- https://git.kernel.org/stable/c/44277c50fdba5019ca25bfad1b71e2561b0de11b
- https://git.kernel.org/stable/c/4b98799e181b4326a613108cf37acc1f55d21b45
- https://git.kernel.org/stable/c/6bfff81286d4491f02dad7814bae5c77c9ad2320
- https://git.kernel.org/stable/c/7941b74ed49b6db25efbef2256ebef843c11a010
- https://git.kernel.org/stable/c/82ae73ac963cee877ce34f7c31b2b456b516e96c
- https://git.kernel.org/stable/c/b642b52d0b50f4d398cb4293f64992d0eed2e2ce
- https://git.kernel.org/stable/c/f3d97b22a708bf9e3f3ac2ba232bcefd0b0c136b
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix qgroup reserve overflow the qgroup limit\n\nWe use extent_changeset->bytes_changed in qgroup_reserve_data() to record\nhow many bytes we set for EXTENT_QGROUP_RESERVED state. Currently the\nbytes_changed is set as \"unsigned int\", and it will overflow if we try to\nfallocate a range larger than 4GiB. The result is we reserve less bytes\nand eventually break the qgroup limit.\n\nUnlike regular buffered/direct write, which we use one changeset for\neach ordered extent, which can never be larger than 256M. For\nfallocate, we use one changeset for the whole range, thus it no longer\nrespects the 256M per extent limit, and caused the problem.\n\nThe following example test script reproduces the problem:\n\n $ cat qgroup-overflow.sh\n #!/bin/bash\n\n DEV=/dev/sdj\n MNT=/mnt/sdj\n\n mkfs.btrfs -f $DEV\n mount $DEV $MNT\n\n # Set qgroup limit to 2GiB.\n btrfs quota enable $MNT\n btrfs qgroup limit 2G $MNT\n\n # Try to fallocate a 3GiB file. This should fail.\n echo\n echo \"Try to fallocate a 3GiB file...\"\n fallocate -l 3G $MNT/3G.file\n\n # Try to fallocate a 5GiB file.\n echo\n echo \"Try to fallocate a 5GiB file...\"\n fallocate -l 5G $MNT/5G.file\n\n # See we break the qgroup limit.\n echo\n sync\n btrfs qgroup show -r $MNT\n\n umount $MNT\n\nWhen running the test:\n\n $ ./qgroup-overflow.sh\n (...)\n\n Try to fallocate a 3GiB file...\n fallocate: fallocate failed: Disk quota exceeded\n\n Try to fallocate a 5GiB file...\n\n qgroupid rfer excl max_rfer\n -------- ---- ---- --------\n 0/5 5.00GiB 5.00GiB 2.00GiB\n\nSince we have no control of how bytes_changed is used, it's better to\nset it to u64."
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"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: corregir el desbordamiento de reserva de qgroup del límite de qgroup Usamos extended_changeset->bytes_changed en qgroup_reserve_data() para registrar cuántos bytes configuramos para el estado EXTENT_QGROUP_RESERVED. Actualmente, bytes_changed está configurado como \"unsigned int\" y se desbordará si intentamos hacer falocación en un rango mayor a 4 GiB. El resultado es que reservamos menos bytes y eventualmente rompemos el límite de qgroup. A diferencia de la escritura directa/en búfer regular, que utilizamos un conjunto de cambios para cada extensión ordenada, que nunca puede ser mayor a 256M. Para falocación, utilizamos un conjunto de cambios para todo el rango, por lo tanto, ya no respeta el límite de 256M por extensión y causó el problema. El siguiente ejemplo de secuencia de comandos de prueba reproduce el problema: $ cat qgroup-overflow.sh #!/bin/bash DEV=/dev/sdj MNT=/mnt/sdj mkfs.btrfs -f $DEV mount $DEV $MNT # Establezca el límite de qgroup en 2 GiB. btrfs quota enable $MNT btrfs qgroup limit 2G $MNT # Intente realizar la operación de fallocate de un archivo de 3 GiB. Esto debería fallar. echo echo \"Intente realizar la operación de fallocate de un archivo de 3 GiB...\" fallocate -l 3G $MNT/3G.file # Intente realizar la operación de fallocate de un archivo de 5 GiB. echo echo \"Intente realizar la operación de fallocate de un archivo de 5 GiB...\" fallocate -l 5G $MNT/5G.file # Vea que rompemos el límite de qgroup. echo sync btrfs qgroup show -r $MNT umount $MNT Al ejecutar la prueba: $ ./qgroup-overflow.sh (...) Intenta fallar un archivo de 3 GiB... fallocate: fallocate falló: Cuota de disco excedida Intenta fallar un archivo de 5 GiB... qgroupid rfer excl max_rfer -------- ---- ---- -------- 0/5 5.00GiB 5.00GiB 2.00GiB Dado que no tenemos control sobre cómo se usa bytes_changed, es mejor configurarlo en u64."
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"lastModified": "2026-08-04T10:17:33.403",
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