GHSA-HVFH-9745-GHHQ
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net
nfsd_file_dispose_list_delayed() defers fput() to nfsd service threads via a per-net freeme queue, preventing the shrinker and GC worker from bearing the cost of closing files (see ffb402596147). However, the queue lives in a separately-allocated struct nfsd_fcache_disposal that is freed by nfsd_free_fcache_disposal_net() during per-net teardown. The global shrinker, laundrette, and fsnotify callbacks can still be inside nfsd_file_dispose_list_delayed() dereferencing that pointer, causing a use-after-free.
Inline the spinlock and freeme list directly into struct nfsd_net (as fcache_dispose_lock and fcache_dispose_list), eliminating the separately allocated struct nfsd_fcache_disposal entirely. These fields now have the same lifetime as the net namespace itself, so there is no dangling pointer to chase.
nfsd_file_cache_start_net() now just initializes the inline fields and cannot fail due to allocation. nfsd_file_cache_shutdown_net() drains the inline list directly instead of freeing a separate struct. The alloc/free helpers are removed.
{
"affected": [],
"aliases": [
"CVE-2026-89682"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:55Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net\n\nnfsd_file_dispose_list_delayed() defers fput() to nfsd service threads\nvia a per-net freeme queue, preventing the shrinker and GC worker from\nbearing the cost of closing files (see ffb402596147). However, the\nqueue lives in a separately-allocated struct nfsd_fcache_disposal that\nis freed by nfsd_free_fcache_disposal_net() during per-net teardown.\nThe global shrinker, laundrette, and fsnotify callbacks can still be\ninside nfsd_file_dispose_list_delayed() dereferencing that pointer,\ncausing a use-after-free.\n\nInline the spinlock and freeme list directly into struct nfsd_net (as\nfcache_dispose_lock and fcache_dispose_list), eliminating the separately\nallocated struct nfsd_fcache_disposal entirely. These fields now have\nthe same lifetime as the net namespace itself, so there is no dangling\npointer to chase.\n\nnfsd_file_cache_start_net() now just initializes the inline fields and\ncannot fail due to allocation. nfsd_file_cache_shutdown_net() drains\nthe inline list directly instead of freeing a separate struct. The\nalloc/free helpers are removed.",
"id": "GHSA-hvfh-9745-ghhq",
"modified": "2026-09-13T09:32:27Z",
"published": "2026-09-11T21:31:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89682"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ba0ee9e04b7a0356c28d5a2fe445db675d24e572"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cadc9036d5a8209f89e7026ddba7cfb1c716b03c"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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