CVE-2026-64359
Estado: AnalizadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers
Syzbot reported a hung task in nilfs_transaction_begin() where multiple tasks performing chmod() on a nilfs2 mount blocked for over 143 seconds waiting to acquire ns_segctor_sem for read:
The writer holding ns_segctor_sem was a concurrent NILFS_IOCTL_CLEAN_SEGMENTS caller, stuck inside printk while emitting per-element warnings from nilfs_sufile_updatev():
The root cause is that user-supplied segment numbers are not validated before nilfs_clean_segments() begins doing work; the range check on each segnum is performed deep inside the call chain by nilfs_sufile_updatev(), which emits a nilfs_warn() per invalid entry while still holding the segctor lock and the sufile mi_sem.
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Under load (repeated invocations across multiple mounts saturating the global printk path), the cumulative printk latency keeps ns_segctor_sem held long enough to trip the hung_task watchdog, blocking concurrent operations such as chmod() that need ns_segctor_sem for read.
Fix by validating the contents of kbufs[4] in nilfs_clean_segments() immediately after acquiring ns_segctor_sem via nilfs_transaction_lock(). Holding ns_segctor_sem serializes the check against nilfs_ioctl_resize(), which can modify ns_nsegments, so the validation uses a consistent value. Out-of-range segment numbers are rejected with -EINVAL before any segment-cleaning work begins, so the bad entries never reach the per-element diagnostic path inside nilfs_sufile_updatev().
Detalles técnicos trazas, registros y código del informe original
INFO: task syz.0.17:5918 blocked for more than 143 seconds. Call Trace: schedule+0x164/0x360 rwsem_down_read_slowpath+0x6d9/0x940 down_read+0x99/0x2e0 nilfs_transaction_begin+0x364/0x710 fs/nilfs2/segment.c:221 nilfs_setattr+0x124/0x2c0 fs/nilfs2/inode.c:921 notify_change+0xc1a/0xf40 chmod_common+0x273/0x4a0 do_fchmodat+0x12d/0x230 __nilfs_msg+0x373/0x450 fs/nilfs2/super.c:78 nilfs_sufile_updatev+0x21c/0x6d0 fs/nilfs2/sufile.c:186 nilfs_sufile_freev fs/nilfs2/sufile.h:93 [inline] nilfs_free_segments fs/nilfs2/segment.c:1140 [inline] nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1261 [inline] nilfs_segctor_do_construct+0x1f55/0x76c0 nilfs_clean_segments+0x3bd/0xa50 nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:922 [inline] nilfs_ioctl+0x261f/0x2780
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)
CWE
- NVD-CWE-noinfo
Referencias
- https://git.kernel.org/stable/c/0789f0a6710713254a08f3a7d2ecbb6d1cbcf0aa
- https://git.kernel.org/stable/c/0e7a690fe435f8d5ea3feb7c1d8d73ba7e8b8aa9
- https://git.kernel.org/stable/c/223463c488b0554212a94de971ea538eb2805fc7
- https://git.kernel.org/stable/c/286f77d002a337735c0846d7480a82d9cda2aa31
- https://git.kernel.org/stable/c/39607452b1400c7bf748f15122df4d058b768c5b
- https://git.kernel.org/stable/c/3ed388ec3b8922383d1e2d4432d7bd4cbbf8364e
- https://git.kernel.org/stable/c/876c98e0fc65f071680c03c2e2ee3ef7ff9ca078
- https://git.kernel.org/stable/c/d26aef771b4f6923da9f89d6d5b70d8def5853de
JSON original (NVD)
Mostrar
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers\n\nSyzbot reported a hung task in nilfs_transaction_begin() where multiple\ntasks performing chmod() on a nilfs2 mount blocked for over 143 seconds\nwaiting to acquire ns_segctor_sem for read:\n\n INFO: task syz.0.17:5918 blocked for more than 143 seconds.\n Call Trace:\n schedule+0x164/0x360\n rwsem_down_read_slowpath+0x6d9/0x940\n down_read+0x99/0x2e0\n nilfs_transaction_begin+0x364/0x710 fs/nilfs2/segment.c:221\n nilfs_setattr+0x124/0x2c0 fs/nilfs2/inode.c:921\n notify_change+0xc1a/0xf40\n chmod_common+0x273/0x4a0\n do_fchmodat+0x12d/0x230\n\nThe writer holding ns_segctor_sem was a concurrent\nNILFS_IOCTL_CLEAN_SEGMENTS caller, stuck inside printk while emitting\nper-element warnings from nilfs_sufile_updatev():\n\n __nilfs_msg+0x373/0x450 fs/nilfs2/super.c:78\n nilfs_sufile_updatev+0x21c/0x6d0 fs/nilfs2/sufile.c:186\n nilfs_sufile_freev fs/nilfs2/sufile.h:93 [inline]\n nilfs_free_segments fs/nilfs2/segment.c:1140 [inline]\n nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1261 [inline]\n nilfs_segctor_do_construct+0x1f55/0x76c0\n nilfs_clean_segments+0x3bd/0xa50\n nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:922 [inline]\n nilfs_ioctl+0x261f/0x2780\n\nThe root cause is that user-supplied segment numbers are not validated\nbefore nilfs_clean_segments() begins doing work; the range check on\neach segnum is performed deep inside the call chain by\nnilfs_sufile_updatev(), which emits a nilfs_warn() per invalid entry\nwhile still holding the segctor lock and the sufile mi_sem. Under load\n(repeated invocations across multiple mounts saturating the global\nprintk path), the cumulative printk latency keeps ns_segctor_sem held\nlong enough to trip the hung_task watchdog, blocking concurrent\noperations such as chmod() that need ns_segctor_sem for read.\n\nFix by validating the contents of kbufs[4] in nilfs_clean_segments()\nimmediately after acquiring ns_segctor_sem via nilfs_transaction_lock().\nHolding ns_segctor_sem serializes the check against\nnilfs_ioctl_resize(), which can modify ns_nsegments, so the validation\nuses a consistent value. Out-of-range segment numbers are rejected\nwith -EINVAL before any segment-cleaning work begins, so the bad\nentries never reach the per-element diagnostic path inside\nnilfs_sufile_updatev()."
}
],
"lastModified": "2026-09-04T15:57:39.937",
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