CVE-2022-49834 (GCVE-0-2022-49834)
Vulnerability from cvelistv5
Published
2025-05-01 14:09
Modified
2025-05-04 08:46
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix use-after-free bug of ns_writer on remount If a nilfs2 filesystem is downgraded to read-only due to metadata corruption on disk and is remounted read/write, or if emergency read-only remount is performed, detaching a log writer and synchronizing the filesystem can be done at the same time. In these cases, use-after-free of the log writer (hereinafter nilfs->ns_writer) can happen as shown in the scenario below: Task1 Task2 -------------------------------- ------------------------------ nilfs_construct_segment nilfs_segctor_sync init_wait init_waitqueue_entry add_wait_queue schedule nilfs_remount (R/W remount case) nilfs_attach_log_writer nilfs_detach_log_writer nilfs_segctor_destroy kfree finish_wait _raw_spin_lock_irqsave __raw_spin_lock_irqsave do_raw_spin_lock debug_spin_lock_before <-- use-after-free While Task1 is sleeping, nilfs->ns_writer is freed by Task2. After Task1 waked up, Task1 accesses nilfs->ns_writer which is already freed. This scenario diagram is based on the Shigeru Yoshida's post [1]. This patch fixes the issue by not detaching nilfs->ns_writer on remount so that this UAF race doesn't happen. Along with this change, this patch also inserts a few necessary read-only checks with superblock instance where only the ns_writer pointer was used to check if the filesystem is read-only.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Version: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nilfs2/segment.c",
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          "product": "Linux",
          "programFiles": [
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            "fs/nilfs2/super.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "4.9.334",
              "versionType": "semver"
            },
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              "status": "unaffected",
              "version": "4.14.300",
              "versionType": "semver"
            },
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              "version": "6.1",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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          "nodes": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: fix use-after-free bug of ns_writer on remount\n\nIf a nilfs2 filesystem is downgraded to read-only due to metadata\ncorruption on disk and is remounted read/write, or if emergency read-only\nremount is performed, detaching a log writer and synchronizing the\nfilesystem can be done at the same time.\n\nIn these cases, use-after-free of the log writer (hereinafter\nnilfs-\u003ens_writer) can happen as shown in the scenario below:\n\n Task1                               Task2\n --------------------------------    ------------------------------\n nilfs_construct_segment\n   nilfs_segctor_sync\n     init_wait\n     init_waitqueue_entry\n     add_wait_queue\n     schedule\n                                     nilfs_remount (R/W remount case)\n\t\t\t\t       nilfs_attach_log_writer\n                                         nilfs_detach_log_writer\n                                           nilfs_segctor_destroy\n                                             kfree\n     finish_wait\n       _raw_spin_lock_irqsave\n         __raw_spin_lock_irqsave\n           do_raw_spin_lock\n             debug_spin_lock_before  \u003c-- use-after-free\n\nWhile Task1 is sleeping, nilfs-\u003ens_writer is freed by Task2.  After Task1\nwaked up, Task1 accesses nilfs-\u003ens_writer which is already freed.  This\nscenario diagram is based on the Shigeru Yoshida\u0027s post [1].\n\nThis patch fixes the issue by not detaching nilfs-\u003ens_writer on remount so\nthat this UAF race doesn\u0027t happen.  Along with this change, this patch\nalso inserts a few necessary read-only checks with superblock instance\nwhere only the ns_writer pointer was used to check if the filesystem is\nread-only."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-05-04T08:46:30.738Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/b2fbf10040216ef5ee270773755fc2f5da65b749"
        },
        {
          "url": "https://git.kernel.org/stable/c/39a3ed68270b079c6b874d4e4727a512b9b4882c"
        },
        {
          "url": "https://git.kernel.org/stable/c/b4736ab5542112fe0a40f140a0a0b072954f34da"
        },
        {
          "url": "https://git.kernel.org/stable/c/9b162e81045266a2d5b44df9dffdf05c54de9cca"
        },
        {
          "url": "https://git.kernel.org/stable/c/4feedde5486c07ea79787839153a71ca71329c7d"
        },
        {
          "url": "https://git.kernel.org/stable/c/afbd1188382a75f6cfe22c0b68533f7f9664f182"
        },
        {
          "url": "https://git.kernel.org/stable/c/b152300d5a1ba4258dacf9916bff20e6a8c7603b"
        },
        {
          "url": "https://git.kernel.org/stable/c/8cccf05fe857a18ee26e20d11a8455a73ffd4efd"
        }
      ],
      "title": "nilfs2: fix use-after-free bug of ns_writer on remount",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2022-49834",
    "datePublished": "2025-05-01T14:09:52.076Z",
    "dateReserved": "2025-05-01T14:05:17.228Z",
    "dateUpdated": "2025-05-04T08:46:30.738Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2022-49834\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-05-01T15:16:06.873\",\"lastModified\":\"2025-05-02T13:53:20.943\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnilfs2: fix use-after-free bug of ns_writer on remount\\n\\nIf a nilfs2 filesystem is downgraded to read-only due to metadata\\ncorruption on disk and is remounted read/write, or if emergency read-only\\nremount is performed, detaching a log writer and synchronizing the\\nfilesystem can be done at the same time.\\n\\nIn these cases, use-after-free of the log writer (hereinafter\\nnilfs-\u003ens_writer) can happen as shown in the scenario below:\\n\\n Task1                               Task2\\n --------------------------------    ------------------------------\\n nilfs_construct_segment\\n   nilfs_segctor_sync\\n     init_wait\\n     init_waitqueue_entry\\n     add_wait_queue\\n     schedule\\n                                     nilfs_remount (R/W remount case)\\n\\t\\t\\t\\t       nilfs_attach_log_writer\\n                                         nilfs_detach_log_writer\\n                                           nilfs_segctor_destroy\\n                                             kfree\\n     finish_wait\\n       _raw_spin_lock_irqsave\\n         __raw_spin_lock_irqsave\\n           do_raw_spin_lock\\n             debug_spin_lock_before  \u003c-- use-after-free\\n\\nWhile Task1 is sleeping, nilfs-\u003ens_writer is freed by Task2.  After Task1\\nwaked up, Task1 accesses nilfs-\u003ens_writer which is already freed.  This\\nscenario diagram is based on the Shigeru Yoshida\u0027s post [1].\\n\\nThis patch fixes the issue by not detaching nilfs-\u003ens_writer on remount so\\nthat this UAF race doesn\u0027t happen.  Along with this change, this patch\\nalso inserts a few necessary read-only checks with superblock instance\\nwhere only the ns_writer pointer was used to check if the filesystem is\\nread-only.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: nilfs2: corrige el error de use-after-free de ns_writer al volver a montar Si un sistema de archivos nilfs2 se degrada a solo lectura debido a la corrupci\u00f3n de metadatos en el disco y se vuelve a montar en modo de lectura/escritura, o si se realiza un remontaje de solo lectura de emergencia, se puede desconectar un escritor de registros y sincronizar el sistema de archivos al mismo tiempo. En estos casos, el use-after-free del escritor de registros (en adelante nilfs-\u0026gt;ns_writer) puede ocurrir como se muestra en el siguiente escenario: Tarea1 Tarea2 -------------------------------- ---------------------------------- nilfs_construct_segment nilfs_segctor_sync init_wait init_waitqueue_entry add_wait_queue schedule nilfs_remount (caso de remontaje de R/W) nilfs_attach_log_writer nilfs_detach_log_writer nilfs_segctor_destroy kfree finish_wait _raw_spin_lock_irqsave __raw_spin_lock_irqsave do_raw_spin_lock debug_spin_lock_before \u0026lt;-- use-after-free Mientras la Tarea1 est\u00e1 en reposo, nilfs-\u0026gt;ns_writer es liberado por la Tarea2. Despu\u00e9s de que la Tarea1 se despierta, la Tarea1 accede a nilfs-\u0026gt;ns_writer que ya est\u00e1 liberado. Este diagrama de escenario se basa en la publicaci\u00f3n de Shigeru Yoshida [1]. Este parche corrige el problema al no desvincular nilfs-\u0026gt;ns_writer al volver a montar, lo que evita que se produzca esta ejecuci\u00f3n UAF. Adem\u00e1s de este cambio, este parche tambi\u00e9n inserta algunas comprobaciones de solo lectura necesarias con la instancia de superbloque, donde solo se usaba el puntero ns_writer para comprobar si el sistema de archivos era de solo lectura.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/39a3ed68270b079c6b874d4e4727a512b9b4882c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4feedde5486c07ea79787839153a71ca71329c7d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8cccf05fe857a18ee26e20d11a8455a73ffd4efd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9b162e81045266a2d5b44df9dffdf05c54de9cca\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/afbd1188382a75f6cfe22c0b68533f7f9664f182\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b152300d5a1ba4258dacf9916bff20e6a8c7603b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b2fbf10040216ef5ee270773755fc2f5da65b749\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b4736ab5542112fe0a40f140a0a0b072954f34da\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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