CVE-2026-93100
In the Linux kernel, the following vulnerability has been resolved:
fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()
A struct rdtgroup is reference counted via rdtgroup::waitcount. Callers that need the structure to remain valid across a sleep (while waiting on acquiring rdtgroup_mutex) take a reference with rdtgroup_kn_get() and release it with rdtgroup_kn_put().
The release path is intended to serve as the fallback freer: if the count drops to zero and the group has already been marked RDT_DELETED, rdtgroup_kn_put() frees the structure.
The bulk teardown paths free_all_child_rdtgrp() and rmdir_all_sub() resulting from a resctrl directory remove or resctrl fs unmount act as the primary freer: they hold rdtgroup_mutex and free each rdtgroup whose waitcount is zero, otherwise they set RDT_DELETED and leave the freeing to the last waiter.
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These two freers race. rdtgroup_kn_put() commits waitcount == 0 with atomic_dec_and_test() outside rdtgroup_mutex, then reads rdtgroup::flags. Between those two operations a concurrent caller of free_all_child_rdtgrp() or rmdir_all_sub() (which holds the mutex) can observe waitcount == 0 via atomic_read(), call rdtgroup_remove(), and kfree() the structure.
The subsequent read of rdtgroup::flags in rdtgroup_kn_put() is then a use-after-free, and the structure may even be freed twice if the freed memory happens to satisfy the RDT_DELETED flag check.
Replace the bare atomic_dec_and_test() with atomic_dec_and_mutex_lock() so that the decrement-to-zero takes rdtgroup_mutex before the count becomes globally visible. The inspection of rdtgroup::flags then runs under the same mutex held by the bulk freers, making the two paths mutually exclusive.
The common case where the count does not reach zero remains lock-free. Defer kernfs_unbreak_active_protection() until after the mutex is dropped since kernfs active protections functionally wrap rdtgroup_mutex. Remove resource group, which in turn drops its kernfs reference, after kernfs protection is restored.
Detalles técnicos trazas, registros y código del informe original
[ bp: Split the commit messsages into smaller, easier-parseable paragraphs. ]
CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 10
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-93100",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
"lessThan": "ae69f936e8ffed553d899ba4c02f8a7461a89e54",
"versionType": "git"
},
{
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
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{
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"versionType": "git"
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{
"status": "affected",
"version": "d20edc0bca5577bab38acb5b190619c922ddebf8",
"versionType": "git"
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{
"status": "affected",
"version": "1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625",
"versionType": "git"
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{
"status": "affected",
"version": "40300f986e47dbc8f1d02e5080385f5cf9f85f70",
"versionType": "git"
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{
"status": "affected",
"version": "b5a4949897ebada8132d54c93208989482503103",
"versionType": "git"
},
{
"status": "affected",
"version": "4.14.170",
"lessThan": "4.15",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.19.102",
"lessThan": "4.20",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.4.18",
"lessThan": "5.5",
"versionType": "semver"
},
{
"status": "affected",
"version": "5.5.2",
"lessThan": "5.6",
"versionType": "semver"
}
],
"programFiles": [
"fs/resctrl/rdtgroup.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.6"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.6",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.18.52",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.6",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/resctrl/rdtgroup.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-17T17:18:04.223",
"references": [
{
"url": "https://git.kernel.org/stable/c/4c593c62c1499665baebbb41b70e2c9b7e947b86",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ae69f936e8ffed553d899ba4c02f8a7461a89e54",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/f5bcf539484d2d604c2f2330e09487ea090b21c7",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/resctrl: Prevent use-after-free in rdtgroup_kn_put()\n\nA struct rdtgroup is reference counted via rdtgroup::waitcount. Callers that\nneed the structure to remain valid across a sleep (while waiting on acquiring\nrdtgroup_mutex) take a reference with rdtgroup_kn_get() and release it with\nrdtgroup_kn_put().\n\nThe release path is intended to serve as the fallback freer: if the count\ndrops to zero and the group has already been marked RDT_DELETED,\nrdtgroup_kn_put() frees the structure.\n\nThe bulk teardown paths free_all_child_rdtgrp() and rmdir_all_sub() resulting\nfrom a resctrl directory remove or resctrl fs unmount act as the primary\nfreer: they hold rdtgroup_mutex and free each rdtgroup whose waitcount is\nzero, otherwise they set RDT_DELETED and leave the freeing to the last waiter.\n\nThese two freers race. rdtgroup_kn_put() commits waitcount == 0 with\natomic_dec_and_test() outside rdtgroup_mutex, then reads rdtgroup::flags.\nBetween those two operations a concurrent caller of free_all_child_rdtgrp()\nor rmdir_all_sub() (which holds the mutex) can observe waitcount == 0 via\natomic_read(), call rdtgroup_remove(), and kfree() the structure.\n\nThe subsequent read of rdtgroup::flags in rdtgroup_kn_put() is then\na use-after-free, and the structure may even be freed twice if the freed\nmemory happens to satisfy the RDT_DELETED flag check.\n\nReplace the bare atomic_dec_and_test() with atomic_dec_and_mutex_lock() so\nthat the decrement-to-zero takes rdtgroup_mutex before the count becomes\nglobally visible. The inspection of rdtgroup::flags then runs under the same\nmutex held by the bulk freers, making the two paths mutually exclusive.\n\nThe common case where the count does not reach zero remains lock-free. Defer\nkernfs_unbreak_active_protection() until after the mutex is dropped since\nkernfs active protections functionally wrap rdtgroup_mutex. Remove resource\ngroup, which in turn drops its kernfs reference, after kernfs protection is\nrestored.\n\n [ bp: Split the commit messsages into smaller, easier-parseable paragraphs. ]"
}
],
"lastModified": "2026-09-17T17:18:04.223",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}