CVE-2024-47679
Estado: ModificadaMedia (4.7)—
In the Linux kernel, the following vulnerability has been resolved:
vfs: fix race between evice_inodes() and find_inode()&iput()
Hi, all
Recently I noticed a bug[1] in btrfs, after digged it into and I believe it'a race in vfs.
Let's assume there's a inode (ie ino 261) with i_count 1 is called by iput(), and there's a concurrent thread calling generic_shutdown_super().
Now, we have two threads simultaneously evicting the same inode, which may trigger the BUG(inode->i_state & I_CLEAR) statement both within clear_inode() and iput().
To fix the bug, recheck the inode->i_count after holding i_lock. Because in the most scenarios, the first check is valid, and the overhead of spin_lock() can be reduced.
Leer descripción completaMostrar menos
If there is any misunderstanding, please let me know, thanks.
[1]: https://lore.kernel.org/linux-btrfs/000000000000eabe1d0619c48986@google.com/ [2]: The reason might be 1. SB_ACTIVE was removed or 2. mapping_shrinkable() return false when I reproduced the bug.
Detalles técnicos trazas, registros y código del informe original
cpu0: cpu1:
iput() // i_count is 1
->spin_lock(inode)
->dec i_count to 0
->iput_final() generic_shutdown_super()
->__inode_add_lru() ->evict_inodes()
// cause some reason[2] ->if (atomic_read(inode->i_count)) continue;
// return before // inode 261 passed the above check
// list_lru_add_obj() // and then schedule out
->spin_unlock()
// note here: the inode 261
// was still at sb list and hash list,
// and I_FREEING|I_WILL_FREE was not been set
btrfs_iget()
// after some function calls
->find_inode()
// found the above inode 261
->spin_lock(inode)
// check I_FREEING|I_WILL_FREE
// and passed
->__iget()
->spin_unlock(inode) // schedule back
->spin_lock(inode)
// check (I_NEW|I_FREEING|I_WILL_FREE) flags,
// passed and set I_FREEING
iput() ->spin_unlock(inode)
->spin_lock(inode) ->evict()
// dec i_count to 0
->iput_final()
->spin_unlock()
->evict()CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 4.7
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.20%
- Percentil entre todas las CVEs puntuadas: 9
- 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-362
Referencias
- https://git.kernel.org/stable/c/0eed942bc65de1f93eca7bda51344290f9c573bb
- https://git.kernel.org/stable/c/0f8a5b6d0dafa4f533ac82e98f8b812073a7c9d1
- https://git.kernel.org/stable/c/3721a69403291e2514d13a7c3af50a006ea1153b
- https://git.kernel.org/stable/c/47a68c75052a660e4c37de41e321582ec9496195
- https://git.kernel.org/stable/c/489faddb1ae75b0e1a741fe5ca2542a2b5e794a5
- https://git.kernel.org/stable/c/540fb13120c9eab3ef203f90c00c8e69f37449d1
- https://git.kernel.org/stable/c/6c857fb12b9137fee574443385d53914356bbe11
- https://git.kernel.org/stable/c/6cc13a80a26e6b48f78c725c01b91987d61563ef
- https://git.kernel.org/stable/c/88b1afbf0f6b221f6c5bb66cc80cd3b38d696687
- 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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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvfs: fix race between evice_inodes() and find_inode()&iput()\n\nHi, all\n\nRecently I noticed a bug[1] in btrfs, after digged it into\nand I believe it'a race in vfs.\n\nLet's assume there's a inode (ie ino 261) with i_count 1 is\ncalled by iput(), and there's a concurrent thread calling\ngeneric_shutdown_super().\n\ncpu0: cpu1:\niput() // i_count is 1\n ->spin_lock(inode)\n ->dec i_count to 0\n ->iput_final() generic_shutdown_super()\n ->__inode_add_lru() ->evict_inodes()\n // cause some reason[2] ->if (atomic_read(inode->i_count)) continue;\n // return before // inode 261 passed the above check\n // list_lru_add_obj() // and then schedule out\n ->spin_unlock()\n// note here: the inode 261\n// was still at sb list and hash list,\n// and I_FREEING|I_WILL_FREE was not been set\n\nbtrfs_iget()\n // after some function calls\n ->find_inode()\n // found the above inode 261\n ->spin_lock(inode)\n // check I_FREEING|I_WILL_FREE\n // and passed\n ->__iget()\n ->spin_unlock(inode) // schedule back\n ->spin_lock(inode)\n // check (I_NEW|I_FREEING|I_WILL_FREE) flags,\n // passed and set I_FREEING\niput() ->spin_unlock(inode)\n ->spin_lock(inode)\t\t\t ->evict()\n // dec i_count to 0\n ->iput_final()\n ->spin_unlock()\n ->evict()\n\nNow, we have two threads simultaneously evicting\nthe same inode, which may trigger the BUG(inode->i_state & I_CLEAR)\nstatement both within clear_inode() and iput().\n\nTo fix the bug, recheck the inode->i_count after holding i_lock.\nBecause in the most scenarios, the first check is valid, and\nthe overhead of spin_lock() can be reduced.\n\nIf there is any misunderstanding, please let me know, thanks.\n\n[1]: https://lore.kernel.org/linux-btrfs/000000000000eabe1d0619c48986@google.com/\n[2]: The reason might be 1. SB_ACTIVE was removed or 2. mapping_shrinkable()\nreturn false when I reproduced the bug."
},
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"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: vfs: arregla la ejecución entre evice_inodes() y find_inode()&iput() Hola a todos Recientemente noté un error[1] en btrfs, después de investigarlo y creo que es una ejecución en vfs. Supongamos que hay un inodo (es decir, ino 261) con i_count 1 que es llamado por iput(), y hay un hilo concurrente que llama a generic_shutdown_super(). cpu0: cpu1: iput() // i_count es 1 ->spin_lock(inode) ->dec i_count a 0 ->iput_final() generic_shutdown_super() ->__inode_add_lru() ->evict_inodes() // por alguna razón[2] ->if (atomic_read(inode->i_count)) continue; // regresar antes // el inodo 261 pasó la verificación anterior // list_lru_add_obj() // y luego programar la salida ->spin_unlock() // nota aquí: el inodo 261 // todavía estaba en la lista sb y la lista hash, // y I_FREEING|I_WILL_FREE no se había establecido btrfs_iget() // después de algunas llamadas de función ->find_inode() // encontró el inodo 261 anterior ->spin_lock(inode) // verificó I_FREEING|I_WILL_FREE // y pasó ->__iget() ->spin_unlock(inode) // programó de regreso ->spin_lock(inode) // verificó los indicadores (I_NEW|I_FREEING|I_WILL_FREE), // pasó y estableció I_FREEING iput() ->spin_unlock(inode) ->spin_lock(inode) ->evict() // dec i_count a 0 ->iput_final() ->spin_unlock() ->evict() Ahora, tenemos dos subprocesos expulsando simultáneamente el mismo inodo, lo que puede activar la declaración BUG(inode->i_state & I_CLEAR) tanto dentro de clear_inode() como de iput(). Para corregir el error, vuelva a verificar inode->i_count después de mantener i_lock. Porque en la mayoría de los escenarios, la primera verificación es válida y se puede reducir la sobrecarga de spin_lock(). Si hay algún malentendido, hágamelo saber, gracias. [1]: https://lore.kernel.org/linux-btrfs/000000000000eabe1d0619c48986@google.com/ [2]: La razón podría ser 1. SB_ACTIVE fue eliminado o 2. mapping_shrinkable() devolvió falso cuando reproduje el error."
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"lastModified": "2026-08-04T11:20:39.413",
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