FKIE_CVE-2023-54276

Vulnerability from fkie_nvd - Published: 2025-12-30 13:16 - Updated: 2026-06-17 06:47
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: move init of percpu reply_cache_stats counters back to nfsd_init_net Commit f5f9d4a314da ("nfsd: move reply cache initialization into nfsd startup") moved the initialization of the reply cache into nfsd startup, but didn't account for the stats counters, which can be accessed before nfsd is ever started. The result can be a NULL pointer dereference when someone accesses /proc/fs/nfsd/reply_cache_stats while nfsd is still shut down. This is a regression and a user-triggerable oops in the right situation: - non-x86_64 arch - /proc/fs/nfsd is mounted in the namespace - nfsd is not started in the namespace - unprivileged user calls "cat /proc/fs/nfsd/reply_cache_stats" Although this is easy to trigger on some arches (like aarch64), on x86_64, calling this_cpu_ptr(NULL) evidently returns a pointer to the fixed_percpu_data. That struct looks just enough like a newly initialized percpu var to allow nfsd_reply_cache_stats_show to access it without Oopsing. Move the initialization of the per-net+per-cpu reply-cache counters back into nfsd_init_net, while leaving the rest of the reply cache allocations to be done at nfsd startup time. Kudos to Eirik who did most of the legwork to track this down.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3025d489f9c8984d1bf5916c4a20097ed80fca5c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/66a178177b2b3bb1d71e854c5e7bbb320eb0e566
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/768c408594b52d8531e1a8ab62e5620c19213e73
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8549384d0f65981761fe2077d04fa2a8d37b54e0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ed9ab7346e908496816cffdecd46932035f66e2e
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/cache.h",
            "fs/nfsd/nfscache.c",
            "fs/nfsd/nfsctl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "3025d489f9c8984d1bf5916c4a20097ed80fca5c",
              "status": "affected",
              "version": "4e18b58b106e34ac69d3052dd91f520bd83cf2fc",
              "versionType": "git"
            },
            {
              "lessThan": "8549384d0f65981761fe2077d04fa2a8d37b54e0",
              "status": "affected",
              "version": "70fdee548c036c6bdb496f284c9e78f1654b6dd0",
              "versionType": "git"
            },
            {
              "lessThan": "66a178177b2b3bb1d71e854c5e7bbb320eb0e566",
              "status": "affected",
              "version": "e7e571ed4ec7bb50136233d8e7b986efef2af8c1",
              "versionType": "git"
            },
            {
              "lessThan": "768c408594b52d8531e1a8ab62e5620c19213e73",
              "status": "affected",
              "version": "f5f9d4a314da88c0a5faa6d168bf69081b7a25ae",
              "versionType": "git"
            },
            {
              "lessThan": "ed9ab7346e908496816cffdecd46932035f66e2e",
              "status": "affected",
              "version": "f5f9d4a314da88c0a5faa6d168bf69081b7a25ae",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/cache.h",
            "fs/nfsd/nfscache.c",
            "fs/nfsd/nfsctl.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.3"
            },
            {
              "lessThan": "6.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.4.*",
              "status": "unaffected",
              "version": "6.4.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.5",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: move init of percpu reply_cache_stats counters back to nfsd_init_net\n\nCommit f5f9d4a314da (\"nfsd: move reply cache initialization into nfsd\nstartup\") moved the initialization of the reply cache into nfsd startup,\nbut didn\u0027t account for the stats counters, which can be accessed before\nnfsd is ever started. The result can be a NULL pointer dereference when\nsomeone accesses /proc/fs/nfsd/reply_cache_stats while nfsd is still\nshut down.\n\nThis is a regression and a user-triggerable oops in the right situation:\n\n- non-x86_64 arch\n- /proc/fs/nfsd is mounted in the namespace\n- nfsd is not started in the namespace\n- unprivileged user calls \"cat /proc/fs/nfsd/reply_cache_stats\"\n\nAlthough this is easy to trigger on some arches (like aarch64), on\nx86_64, calling this_cpu_ptr(NULL) evidently returns a pointer to the\nfixed_percpu_data. That struct looks just enough like a newly\ninitialized percpu var to allow nfsd_reply_cache_stats_show to access\nit without Oopsing.\n\nMove the initialization of the per-net+per-cpu reply-cache counters\nback into nfsd_init_net, while leaving the rest of the reply cache\nallocations to be done at nfsd startup time.\n\nKudos to Eirik who did most of the legwork to track this down."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnfsd: mover la inicializaci\u00f3n de los contadores percpu reply_cache_stats de vuelta a nfsd_init_net\n\nEl commit f5f9d4a314da (\u0027nfsd: mover la inicializaci\u00f3n de la cach\u00e9 de respuestas al inicio de nfsd\u0027) movi\u00f3 la inicializaci\u00f3n de la cach\u00e9 de respuestas al inicio de nfsd, pero no tuvo en cuenta los contadores de estad\u00edsticas, los cuales pueden ser accedidos antes de que nfsd se inicie. El resultado puede ser una desreferencia de puntero NULL cuando alguien accede a /proc/fs/nfsd/reply_cache_stats mientras nfsd a\u00fan est\u00e1 apagado.\n\nEsto es una regresi\u00f3n y un oops activable por el usuario en la situaci\u00f3n correcta:\n\n- arquitectura que no sea x86_64\n- /proc/fs/nfsd est\u00e1 montado en el espacio de nombres\n- nfsd no est\u00e1 iniciado en el espacio de nombres\n- usuario sin privilegios llama a \u0027cat /proc/fs/nfsd/reply_cache_stats\u0027\n\nAunque esto es f\u00e1cil de activar en algunas arquitecturas (como aarch64), en x86_64, llamar a this_cpu_ptr(NULL) evidentemente devuelve un puntero a los fixed_percpu_data. Esa estructura se parece lo suficiente a una variable percpu reci\u00e9n inicializada para permitir que nfsd_reply_cache_stats_show acceda a ella sin causar un Oops.\n\nMover la inicializaci\u00f3n de los contadores de cach\u00e9 de respuestas por-red+por-cpu de vuelta a nfsd_init_net, mientras se deja el resto de las asignaciones de la cach\u00e9 de respuestas para ser realizadas en el momento de inicio de nfsd.\n\nFelicitaciones a Eirik quien hizo la mayor parte del trabajo preliminar para rastrear esto."
    }
  ],
  "id": "CVE-2023-54276",
  "lastModified": "2026-06-17T06:47:08.507",
  "metrics": {},
  "published": "2025-12-30T13:16:16.537",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/3025d489f9c8984d1bf5916c4a20097ed80fca5c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/66a178177b2b3bb1d71e854c5e7bbb320eb0e566"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/768c408594b52d8531e1a8ab62e5620c19213e73"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8549384d0f65981761fe2077d04fa2a8d37b54e0"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ed9ab7346e908496816cffdecd46932035f66e2e"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Deferred"
}



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