CVE-2026-89540

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: init gssp_lock before publishing proc entry create_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy via proc_create_data() before init_gssp_clnt() runs mutex_init() on sn->gssp_lock. Once the dentry is linked under proc_subdir_lock it is immediately reachable from userspace, so a write that lands in the window drives set_gssp_clnt() into mutex_lock() on a zero-initialized struct mutex. create_use_gss_proxy_proc_entry(net) proc_create_data("use-gss-proxy", ...) /* dentry live */ init_gssp_clnt(sn) mutex_init(&sn->gssp_lock) /* too late */ write_gssp() set_gssp_clnt(net) mutex_lock(&sn->gssp_lock) /* uninitialized */ gssp_rpc_create(...) sn->gssp_clnt = clnt mutex_unlock(&sn->gssp_lock) The window spans only the two statements between proc_create_data() returning and init_gssp_clnt(), so a writer reaches it only if the registering thread is preempted there while another task is already opening the freshly published file. register_pernet_subsys() runs in preemptible context under pernet_ops_rwsem, so that preemption is possible, and the window widens on auth_rpcgss module load, when the proc entry is created for every live net namespace whose tasks are already running. A writer that wins the race locks a zero-filled struct mutex. On CONFIG_DEBUG_MUTEXES the missing magic value trips a "lock used without init" splat; on a production kernel the fast path acquires the lock via CMPXCHG(owner, 0, current). In the latter case a second writer that arrives before init_gssp_clnt() re-zeroes owner can enter set_gssp_clnt() concurrently, shut down the first writer's clnt while it is still in use, and leak the loser's clnt. Fix by initializing sn->gssp_lock in sunrpc_init_net() so its lifetime matches the sunrpc_net it lives in. sn->gssp_clnt is already NULL from the kzalloc that backs net_generic storage, so the lazy helper is no longer needed; drop init_gssp_clnt(), its prototype, and the call from create_use_gss_proxy_proc_entry(). sunrpc.ko is a build-time dependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on every netns before any auth_gss pernet init can publish the proc entry.

Severity

HIGH

CVSS score

7.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-09-11 20:19:37.097000

Last modified

2026-10-19 09:17:48.820000

View original CVE JSON

{
  "id": "CVE-2026-89540",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-09-11T20:19:37.097",
  "lastModified": "2026-10-19T09:17:48.820",
  "vulnStatus": "Received",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsunrpc: init gssp_lock before publishing proc entry\n\ncreate_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy\nvia proc_create_data() before init_gssp_clnt() runs mutex_init() on\nsn->gssp_lock.  Once the dentry is linked under proc_subdir_lock it is\nimmediately reachable from userspace, so a write that lands in the\nwindow drives set_gssp_clnt() into mutex_lock() on a zero-initialized\nstruct mutex.\n\n    create_use_gss_proxy_proc_entry(net)\n      proc_create_data(\"use-gss-proxy\", ...)   /* dentry live */\n      init_gssp_clnt(sn)\n        mutex_init(&sn->gssp_lock)             /* too late */\n\n    write_gssp()\n      set_gssp_clnt(net)\n        mutex_lock(&sn->gssp_lock)             /* uninitialized */\n        gssp_rpc_create(...)\n        sn->gssp_clnt = clnt\n        mutex_unlock(&sn->gssp_lock)\n\nThe window spans only the two statements between proc_create_data()\nreturning and init_gssp_clnt(), so a writer reaches it only if the\nregistering thread is preempted there while another task is already\nopening the freshly published file.  register_pernet_subsys() runs in\npreemptible context under pernet_ops_rwsem, so that preemption is\npossible, and the window widens on auth_rpcgss module load, when the\nproc entry is created for every live net namespace whose tasks are\nalready running.  A writer that wins the race locks a zero-filled\nstruct mutex.  On CONFIG_DEBUG_MUTEXES the missing magic value trips a\n\"lock used without init\" splat; on a production kernel the fast path\nacquires the lock via CMPXCHG(owner, 0, current).  In the latter case\na second writer that arrives before init_gssp_clnt() re-zeroes owner\ncan enter set_gssp_clnt() concurrently, shut down the first writer's\nclnt while it is still in use, and leak the loser's clnt.\n\nFix by initializing sn->gssp_lock in sunrpc_init_net() so its lifetime\nmatches the sunrpc_net it lives in.  sn->gssp_clnt is already NULL from\nthe kzalloc that backs net_generic storage, so the lazy helper is no\nlonger needed; drop init_gssp_clnt(), its prototype, and the call from\ncreate_use_gss_proxy_proc_entry().  sunrpc.ko is a build-time\ndependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on\nevery netns before any auth_gss pernet init can publish the proc\nentry."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "net/sunrpc/auth_gss/gss_rpc_upcall.c",
            "net/sunrpc/auth_gss/gss_rpc_upcall.h",
            "net/sunrpc/auth_gss/svcauth_gss.c",
            "net/sunrpc/sunrpc_syms.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "030d794bf49855f5e2a9e8dfbfad34211d1eb08b",
              "lessThan": "159a4fab7170badd6c4a553aef81cac079d6f4ee",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "030d794bf49855f5e2a9e8dfbfad34211d1eb08b",
              "lessThan": "b3526ae3351968f6726bcbe25d8d09973ad79109",
              "versionType": "git",
              "status": "affected"
            },
            {
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              "lessThan": "7f5bcdc8da15077ebe846c2756a5a17741021410",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "030d794bf49855f5e2a9e8dfbfad34211d1eb08b",
              "lessThan": "89c8e0733e8c46b7973503f15b1b31a8587d8030",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "030d794bf49855f5e2a9e8dfbfad34211d1eb08b",
              "lessThan": "f15b87521168c2a92cb1931f532cba422f856f01",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "030d794bf49855f5e2a9e8dfbfad34211d1eb08b",
              "lessThan": "edeefb111d6181a4aa278f415b005efe284b9489",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "030d794bf49855f5e2a9e8dfbfad34211d1eb08b",
              "lessThan": "3f019571928b269feebcff59926ec13294215e0e",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "030d794bf49855f5e2a9e8dfbfad34211d1eb08b",
              "lessThan": "5ce1ed6159731a41fdd0b03eedbed4e147036a5a",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "net/sunrpc/auth_gss/gss_rpc_upcall.c",
            "net/sunrpc/auth_gss/gss_rpc_upcall.h",
            "net/sunrpc/auth_gss/svcauth_gss.c",
            "net/sunrpc/sunrpc_syms.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "3.10",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "3.10",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.10.270",
              "lessThanOrEqual": "5.10.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.221",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.188",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.157",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.109",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.50",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2.4",
              "lessThanOrEqual": "7.2.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.3",
              "lessThanOrEqual": "*",
              "versionType": "original_commit_for_fix",
              "status": "unaffected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "attackVector": "LOCAL",
          "attackComplexity": "LOW",
          "privilegesRequired": "LOW",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-16T19:23:23.496498Z",
          "id": "CVE-2026-89540",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/159a4fab7170badd6c4a553aef81cac079d6f4ee",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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}