CVE-2021-47637
Estado: ModificadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
ubifs: Fix deadlock in concurrent rename whiteout and inode writeback
, are caused by concurrent rename whiteout and inode writeback processes: rename_whiteout(Thread 1) wb_workfn(Thread2) ubifs_rename do_rename lock_4_inodes (Hold ui_mutex) ubifs_budget_space make_free_space shrink_liability __writeback_inodes_sb_nr bdi_split_work_to_wbs (Queue new wb work) wb_do_writeback(wb work) __writeback_single_inode ubifs_write_inode LOCK(ui_mutex) ↑ wb_wait_for_completion (Wait wb work) <-- deadlock!
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Fix it by doing whiteout space budget before locking ubifs inodes. BTW, it also fixes wrong goto tag 'out_release' in whiteout budget error handling path(It should at least recover dir i_size and unlock 4 ubifs inodes).
Detalles técnicos trazas, registros y código del informe original
Following hung tasks:
[ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132
[ 77.028820] Call Trace:
[ 77.029027] schedule+0x8c/0x1b0
[ 77.029067] mutex_lock+0x50/0x60
[ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs]
[ 77.029117] __writeback_single_inode+0x43c/0x570
[ 77.029128] writeback_sb_inodes+0x259/0x740
[ 77.029148] wb_writeback+0x107/0x4d0
[ 77.029163] wb_workfn+0x162/0x7b0
[ 92.390442] task:aa state:D stack: 0 pid: 1506
[ 92.390448] Call Trace:
[ 92.390458] schedule+0x8c/0x1b0
[ 92.390461] wb_wait_for_completion+0x82/0xd0
[ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110
[ 92.390472] writeback_inodes_sb_nr+0x14/0x20
[ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs]
[ 92.390503] do_rename.cold+0x7f/0x187 [ubifs]
[ 92.390549] ubifs_rename+0x8b/0x180 [ubifs]
[ 92.390571] vfs_rename+0xdb2/0x1170
[ 92.390580] do_renameat2+0x554/0x770
Reproducer (Detail program in [Link]):
1. SYS_renameat2("/mp/dir/file", "/mp/dir/whiteout", RENAME_WHITEOUT)
2. Consume out of space before kernel(mdelay) doing budget for whiteoutCVSS
- 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: 0.19%
- Percentil entre todas las CVEs puntuadas: 8
- 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-667
- CWE-667
Referencias
- https://git.kernel.org/stable/c/37bdf1ad592555ecda1d55b89f6e393e4c0589d1
- https://git.kernel.org/stable/c/70e9090acc32348cedc5def0cd6d5c126efc97b9
- https://git.kernel.org/stable/c/83e42a78428fc354f5e2049935b84c8d8d29b787
- https://git.kernel.org/stable/c/8b278c8dcfb565cb65eceb62a38cbf7a7c326db5
- https://git.kernel.org/stable/c/9dddc8211430fb851ddf0b168e3a00c6f66cc185
- https://git.kernel.org/stable/c/afd427048047e8efdedab30e8888044e2be5aa9c
- https://git.kernel.org/stable/c/c58af8564a7b08757173009030b74baf4b2b762b
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nubifs: Fix deadlock in concurrent rename whiteout and inode writeback\n\nFollowing hung tasks:\n[ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132\n[ 77.028820] Call Trace:\n[ 77.029027] schedule+0x8c/0x1b0\n[ 77.029067] mutex_lock+0x50/0x60\n[ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs]\n[ 77.029117] __writeback_single_inode+0x43c/0x570\n[ 77.029128] writeback_sb_inodes+0x259/0x740\n[ 77.029148] wb_writeback+0x107/0x4d0\n[ 77.029163] wb_workfn+0x162/0x7b0\n\n[ 92.390442] task:aa state:D stack: 0 pid: 1506\n[ 92.390448] Call Trace:\n[ 92.390458] schedule+0x8c/0x1b0\n[ 92.390461] wb_wait_for_completion+0x82/0xd0\n[ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110\n[ 92.390472] writeback_inodes_sb_nr+0x14/0x20\n[ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs]\n[ 92.390503] do_rename.cold+0x7f/0x187 [ubifs]\n[ 92.390549] ubifs_rename+0x8b/0x180 [ubifs]\n[ 92.390571] vfs_rename+0xdb2/0x1170\n[ 92.390580] do_renameat2+0x554/0x770\n\n, are caused by concurrent rename whiteout and inode writeback processes:\n\trename_whiteout(Thread 1)\t wb_workfn(Thread2)\nubifs_rename\n do_rename\n lock_4_inodes (Hold ui_mutex)\n ubifs_budget_space\n make_free_space\n shrink_liability\n\t __writeback_inodes_sb_nr\n\t bdi_split_work_to_wbs (Queue new wb work)\n\t\t\t\t\t wb_do_writeback(wb work)\n\t\t\t\t\t\t__writeback_single_inode\n\t\t\t\t\t ubifs_write_inode\n\t\t\t\t\t LOCK(ui_mutex)\n\t\t\t\t\t\t\t ↑\n\t wb_wait_for_completion (Wait wb work) <-- deadlock!\n\nReproducer (Detail program in [Link]):\n 1. SYS_renameat2(\"/mp/dir/file\", \"/mp/dir/whiteout\", RENAME_WHITEOUT)\n 2. Consume out of space before kernel(mdelay) doing budget for whiteout\n\nFix it by doing whiteout space budget before locking ubifs inodes.\nBTW, it also fixes wrong goto tag 'out_release' in whiteout budget\nerror handling path(It should at least recover dir i_size and unlock\n4 ubifs inodes)."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad:\n\nubifs: Se corrige interbloqueo en concurrencia de un renombrado con whiteout simultáneo a la escritura del inodo.\n\nTareas colgadas:\n[ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132\n[ 77.028820] Call Trace:\n[ 77.029027] schedule+0x8c/0x1b0\n[ 77.029067] mutex_lock+0x50/0x60\n[ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs]\n[ 77.029117] __writeback_single_inode+0x43c/0x570\n[ 77.029128] writeback_sb_inodes+0x259/0x740\n[ 77.029148] wb_writeback+0x107/0x4d0\n[ 77.029163] wb_workfn+0x162/0x7b0\n\n[ 92.390442] task:aa state:D stack: 0 pid: 1506\n[ 92.390448] Call Trace:\n[ 92.390458] schedule+0x8c/0x1b0\n[ 92.390461] wb_wait_for_completion+0x82/0xd0\n[ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110\n[ 92.390472] writeback_inodes_sb_nr+0x14/0x20\n[ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs]\n[ 92.390503] do_rename.cold+0x7f/0x187 [ubifs]\n[ 92.390549] ubifs_rename+0x8b/0x180 [ubifs]\n[ 92.390571] vfs_rename+0xdb2/0x1170\n[ 92.390580] do_renameat2+0x554/0x770\n\n, ocasionado por procesos simultáneos de renombrado con whiteout y escritura del inodo:\n\trename_whiteout(Thread 1)\t wb_workfn(Thread2)\nubifs_rename\n do_rename\n lock_4_inodes (Hold ui_mutex)\n ubifs_budget_space\n make_free_space\n shrink_liability\n\t __writeback_inodes_sb_nr\n\t bdi_split_work_to_wbs (Queue new wb work)\n\t\t\t\t\t wb_do_writeback(wb work)\n\t\t\t\t\t\t__writeback_single_inode\n\t\t\t\t\t ubifs_write_inode\n\t\t\t\t\t LOCK(ui_mutex)\n\t\t\t\t\t\t\t ?\n\t wb_wait_for_completion (Wait wb work) <-- ¡interbloqueo!\n\nCaso de prueba:\n 1. SYS_renameat2(\"/mp/dir/file\", \"/mp/dir/whiteout\", RENAME_WHITEOUT)\n 2. Consumir todo el espacio antes de que kernel(mdelay) planifique el whiteout\n\nArreglado calculando el espacio de whiteout antes de bloquear los inodos de ubifs.\n\nTambién soluciona etiqueta la etiqueta goto errónea 'out_release' en el flujo de errores\nde la planificación del whiteout (al menos debería recuperar el directorio i_size y desbloquear 4 inodos de ubifs).\n"
}
],
"lastModified": "2026-06-17T04:18:12.670",
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