CVE-2024-49882
Estado: ModificadaAlta (7.8)—
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix double brelse() the buffer of the extents path
In ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has been released, otherwise it may be released twice. An example of what triggers this is as follows:
Finally got the following WARRNING when removing the buffer from lru:
Detalles técnicos trazas, registros y código del informe original
split2 map split1
|--------|-------|--------|
ext4_ext_map_blocks
ext4_ext_handle_unwritten_extents
ext4_split_convert_extents
// path->p_depth == 0
ext4_split_extent
// 1. do split1
ext4_split_extent_at
|ext4_ext_insert_extent
| ext4_ext_create_new_leaf
| ext4_ext_grow_indepth
| le16_add_cpu(&neh->eh_depth, 1)
| ext4_find_extent
| // return -ENOMEM
|// get error and try zeroout
|path = ext4_find_extent
| path->p_depth = 1
|ext4_ext_try_to_merge
| ext4_ext_try_to_merge_up
| path->p_depth = 0
| brelse(path[1].p_bh) ---> not set to NULL here
|// zeroout success
// 2. update path
ext4_find_extent
// 3. do split2
ext4_split_extent_at
ext4_ext_insert_extent
ext4_ext_create_new_leaf
ext4_ext_grow_indepth
le16_add_cpu(&neh->eh_depth, 1)
ext4_find_extent
path[0].p_bh = NULL;
path->p_depth = 1
read_extent_tree_block ---> return err
// path[1].p_bh is still the old value
ext4_free_ext_path
ext4_ext_drop_refs
// path->p_depth == 1
brelse(path[1].p_bh) ---> brelse a buffer twice
============================================
VFS: brelse: Trying to free free buffer
WARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90
CPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716
RIP: 0010:__brelse+0x58/0x90
Call Trace:
<TASK>
__find_get_block+0x6e7/0x810
bdev_getblk+0x2b/0x480
__ext4_get_inode_loc+0x48a/0x1240
ext4_get_inode_loc+0xb2/0x150
ext4_reserve_inode_write+0xb7/0x230
__ext4_mark_inode_dirty+0x144/0x6a0
ext4_ext_insert_extent+0x9c8/0x3230
ext4_ext_map_blocks+0xf45/0x2dc0
ext4_map_blocks+0x724/0x1700
ext4_do_writepages+0x12d6/0x2a70
[...]
============================================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: 0.32%
- Percentil entre todas las CVEs puntuadas: 23
- 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).
🎯 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
T1499.004Application or System Exploitationimpact70 % - Impacto secundario
T1561.002Disk Structure Wipeimpact60 %
Vulnerabilidad de corrupción de memoria en kernel Linux (CWE-415: double-free) con acceso local y privilegios de usuario (AV:L/PR:L). Genera DoS e inestabilidad del sistema de archivos; impactos de disponibilidad e integridad de datos.
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 (2)
CWE
- CWE-415
Referencias
- https://git.kernel.org/stable/c/230ee0535d01478bad9a3037292043f39b9be10b
- https://git.kernel.org/stable/c/32bbb59e3f18facd7201bef110010bf35819b8c3
- https://git.kernel.org/stable/c/68a69cf60660c73990c1875f94a5551600b04775
- https://git.kernel.org/stable/c/7633407ca4ab8be2916ab214eb44ccebc6a50e1a
- https://git.kernel.org/stable/c/78bbc3d15b6f443acb26e94418c445bac940d414
- https://git.kernel.org/stable/c/b6c29c8f3d7cb67b505f3b2f6c242d52298d1f2e
- https://git.kernel.org/stable/c/d4574bda63906bf69660e001470bfe1a0ac524ae
- https://git.kernel.org/stable/c/dcaa6c31134c0f515600111c38ed7750003e1b9c
- https://git.kernel.org/stable/c/f9fd47c9d9548f9e47fa60098eab99dde175401d
- https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
- https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
JSON original (NVD)
Mostrar
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix double brelse() the buffer of the extents path\n\nIn ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has been\nreleased, otherwise it may be released twice. An example of what triggers\nthis is as follows:\n\n split2 map split1\n|--------|-------|--------|\n\next4_ext_map_blocks\n ext4_ext_handle_unwritten_extents\n ext4_split_convert_extents\n // path->p_depth == 0\n ext4_split_extent\n // 1. do split1\n ext4_split_extent_at\n |ext4_ext_insert_extent\n | ext4_ext_create_new_leaf\n | ext4_ext_grow_indepth\n | le16_add_cpu(&neh->eh_depth, 1)\n | ext4_find_extent\n | // return -ENOMEM\n |// get error and try zeroout\n |path = ext4_find_extent\n | path->p_depth = 1\n |ext4_ext_try_to_merge\n | ext4_ext_try_to_merge_up\n | path->p_depth = 0\n | brelse(path[1].p_bh) ---> not set to NULL here\n |// zeroout success\n // 2. update path\n ext4_find_extent\n // 3. do split2\n ext4_split_extent_at\n ext4_ext_insert_extent\n ext4_ext_create_new_leaf\n ext4_ext_grow_indepth\n le16_add_cpu(&neh->eh_depth, 1)\n ext4_find_extent\n path[0].p_bh = NULL;\n path->p_depth = 1\n read_extent_tree_block ---> return err\n // path[1].p_bh is still the old value\n ext4_free_ext_path\n ext4_ext_drop_refs\n // path->p_depth == 1\n brelse(path[1].p_bh) ---> brelse a buffer twice\n\nFinally got the following WARRNING when removing the buffer from lru:\n\n============================================\nVFS: brelse: Trying to free free buffer\nWARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90\nCPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716\nRIP: 0010:__brelse+0x58/0x90\nCall Trace:\n <TASK>\n __find_get_block+0x6e7/0x810\n bdev_getblk+0x2b/0x480\n __ext4_get_inode_loc+0x48a/0x1240\n ext4_get_inode_loc+0xb2/0x150\n ext4_reserve_inode_write+0xb7/0x230\n __ext4_mark_inode_dirty+0x144/0x6a0\n ext4_ext_insert_extent+0x9c8/0x3230\n ext4_ext_map_blocks+0xf45/0x2dc0\n ext4_map_blocks+0x724/0x1700\n ext4_do_writepages+0x12d6/0x2a70\n[...]\n============================================"
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ext4: corregir el doble brelse() del búfer de la ruta de las extensiones En ext4_ext_try_to_merge_up(), establezca path[1].p_bh en NULL después de que se haya liberado, de lo contrario, puede liberarse dos veces. Un ejemplo de lo que desencadena esto es el siguiente: split2 map split1 |--------|-------|--------| ext4_ext_map_blocks ext4_ext_handle_unwritten_extents ext4_split_convert_extents // path->p_depth == 0 ext4_split_extent // 1. hacer split1 ext4_split_extent_at |ext4_ext_insert_extent | ext4_ext_create_new_leaf | ext4_ext_grow_indepth | le16_add_cpu(&neh->eh_depth, 1) | ext4_find_extent | // devuelve -ENOMEM |// obtiene el error e intenta poner a cero |path = ext4_find_extent | path->p_depth = 1 |ext4_ext_try_to_merge | ext4_ext_try_to_merge_up | path->p_depth = 0 | brelse(path[1].p_bh) ---> no establecido en NULL aquí |// puesta a cero exitosa // 2. actualizar ruta ext4_find_extent // 3. hacer split2 ext4_split_extent_at ext4_ext_insert_extent ext4_ext_create_new_leaf ext4_ext_grow_indepth le16_add_cpu(&neh->eh_depth, 1) ext4_find_extent path[0].p_bh = NULL; path->p_depth = 1 read_extent_tree_block ---> return err // path[1].p_bh sigue siendo el valor anterior ext4_free_ext_path ext4_ext_drop_refs // path->p_depth == 1 brelse(path[1].p_bh) ---> brelse un buffer dos veces Finalmente obtuve la siguiente ADVERTENCIA al eliminar el buffer de lru: =============================================== VFS: brelse: Intentando liberar búfer libre ADVERTENCIA: CPU: 2 PID: 72 en fs/buffer.c:1241 __brelse+0x58/0x90 CPU: 2 PID: 72 Comm: kworker/u19:1 No contaminado 6.9.0-dirty #716 RIP: 0010:__brelse+0x58/0x90 Seguimiento de llamadas: __find_get_block+0x6e7/0x810 bdev_getblk+0x2b/0x480 __ext4_get_inode_loc+0x48a/0x1240 ext4_get_inode_loc+0xb2/0x150 ext4_reserve_inode_write+0xb7/0x230 __ext4_mark_inode_dirty+0x144/0x6a0 ext4_ext_insert_extent+0x9c8/0x3230 ext4_ext_map_blocks+0xf45/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ============================================"
}
],
"lastModified": "2026-08-04T11:20:55.380",
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