CVE-2022-50478

Estado: AnalizadaAlta (7.1)—

In the Linux kernel, the following vulnerability has been resolved:

nilfs2: fix shift-out-of-bounds/overflow in nilfs_sb2_bad_offset()

Patch series "nilfs2: fix UBSAN shift-out-of-bounds warnings on mount time".

The first patch fixes a bug reported by syzbot, and the second one fixes the remaining bug of the same kind. Although they are triggered by the same super block data anomaly, I divided it into the above two because the details of the issues and how to fix it are different.

Both are required to eliminate the shift-out-of-bounds issues at mount time.

This patch (of 2):

If the block size exponent information written in an on-disk superblock is corrupted, nilfs_sb2_bad_offset helper function can trigger shift-out-of-bounds warning followed by a kernel panic (if panic_on_warn is set):

Leer descripción completaMostrar menos

In addition, since nilfs_sb2_bad_offset() performs multiplication without considering the upper bound, the computation may overflow if the disk layout parameters are not normal.

This fixes these issues by inserting preliminary sanity checks for those parameters and by converting the comparison from one involving multiplication and left bit-shifting to one using division and right bit-shifting.

Detalles técnicos trazas, registros y código del informe original

 shift exponent 38983 is too large for 64-bit type 'unsigned long long'
 Call Trace:
  <TASK>
  __dump_stack lib/dump_stack.c:88 [inline]
  dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
  ubsan_epilogue lib/ubsan.c:151 [inline]
  __ubsan_handle_shift_out_of_bounds+0x33d/0x3b0 lib/ubsan.c:322
  nilfs_sb2_bad_offset fs/nilfs2/the_nilfs.c:449 [inline]
  nilfs_load_super_block+0xdf5/0xe00 fs/nilfs2/the_nilfs.c:523
  init_nilfs+0xb7/0x7d0 fs/nilfs2/the_nilfs.c:577
  nilfs_fill_super+0xb1/0x5d0 fs/nilfs2/super.c:1047
  nilfs_mount+0x613/0x9b0 fs/nilfs2/super.c:1317
  ...

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Puntuación base: 7.1

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.17%
Percentil entre todas las CVEs puntuadas: 5
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.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation75 %
Impacto principalT1499.004 Application or System Exploitationimpact70 %
Impacto secundarioT1499 Endpoint Denial of Serviceimpact65 %

Acceso local (AV:L) sin interacción del usuario permite escalada mediante corrupción de superbloque en nilfs2, causando pánico del kernel (DoS). CWE-125 (out-of-bounds read) en parámetros de bloque corrupto.

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

Filter Network Traffic Threat Intelligence Program Execution Prevention Application Isolation and Sandboxing Exploit Protection Update Software

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-125

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: fix shift-out-of-bounds/overflow in nilfs_sb2_bad_offset()\n\nPatch series \"nilfs2: fix UBSAN shift-out-of-bounds warnings on mount\ntime\".\n\nThe first patch fixes a bug reported by syzbot, and the second one fixes\nthe remaining bug of the same kind.  Although they are triggered by the\nsame super block data anomaly, I divided it into the above two because the\ndetails of the issues and how to fix it are different.\n\nBoth are required to eliminate the shift-out-of-bounds issues at mount\ntime.\n\n\nThis patch (of 2):\n\nIf the block size exponent information written in an on-disk superblock is\ncorrupted, nilfs_sb2_bad_offset helper function can trigger\nshift-out-of-bounds warning followed by a kernel panic (if panic_on_warn\nis set):\n\n shift exponent 38983 is too large for 64-bit type 'unsigned long long'\n Call Trace:\n  <TASK>\n  __dump_stack lib/dump_stack.c:88 [inline]\n  dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106\n  ubsan_epilogue lib/ubsan.c:151 [inline]\n  __ubsan_handle_shift_out_of_bounds+0x33d/0x3b0 lib/ubsan.c:322\n  nilfs_sb2_bad_offset fs/nilfs2/the_nilfs.c:449 [inline]\n  nilfs_load_super_block+0xdf5/0xe00 fs/nilfs2/the_nilfs.c:523\n  init_nilfs+0xb7/0x7d0 fs/nilfs2/the_nilfs.c:577\n  nilfs_fill_super+0xb1/0x5d0 fs/nilfs2/super.c:1047\n  nilfs_mount+0x613/0x9b0 fs/nilfs2/super.c:1317\n  ...\n\nIn addition, since nilfs_sb2_bad_offset() performs multiplication without\nconsidering the upper bound, the computation may overflow if the disk\nlayout parameters are not normal.\n\nThis fixes these issues by inserting preliminary sanity checks for those\nparameters and by converting the comparison from one involving\nmultiplication and left bit-shifting to one using division and right\nbit-shifting."
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