CVE-2026-89540: Software Security Vulnerability Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gwh2-5395-p8p6",
  "modified" : "2026-09-14T15:32:28Z",
  "published" : "2026-09-11T21:31:31Z",
  "aliases" : [ "CVE-2026-89540" ],
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-89540"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/159a4fab7170badd6c4a553aef81cac079d6f4ee"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/3f019571928b269feebcff59926ec13294215e0e"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/5ce1ed6159731a41fdd0b03eedbed4e147036a5a"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/7f5bcdc8da15077ebe846c2756a5a17741021410"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/89c8e0733e8c46b7973503f15b1b31a8587d8030"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/b3526ae3351968f6726bcbe25d8d09973ad79109"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/edeefb111d6181a4aa278f415b005efe284b9489"
  }, {
    "type" : "WEB",
    "url" : "https://git.kernel.org/stable/c/f15b87521168c2a92cb1931f532cba422f856f01"
  } ],
  "database_specific" : {
    "cwe_ids" : [ ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-09-11T20:19:37Z"
  }
}