CVE-2026-93100 (GCVE-0-2026-93100)
Vulnerability from cvelistv5
Published
2026-09-17 16:11
Modified
2026-10-30 12:35
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
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.
[ bp: Split the commit messsages into smaller, easier-parseable paragraphs. ]
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: b8511ccc75c033f6d54188ea4df7bf1e85778740 Version: b8511ccc75c033f6d54188ea4df7bf1e85778740 Version: b8511ccc75c033f6d54188ea4df7bf1e85778740 Version: b8511ccc75c033f6d54188ea4df7bf1e85778740 Version: b8511ccc75c033f6d54188ea4df7bf1e85778740 Version: b8511ccc75c033f6d54188ea4df7bf1e85778740 Version: d20edc0bca5577bab38acb5b190619c922ddebf8 Version: 1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625 Version: 40300f986e47dbc8f1d02e5080385f5cf9f85f70 Version: b5a4949897ebada8132d54c93208989482503103 Version: 4.14.170 ≤ Version: 4.19.102 ≤ Version: 5.4.18 ≤ Version: 5.5.2 ≤ |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/resctrl/rdtgroup.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "906b3044dbf7c38cc411f7cf457c811363161e3b",
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
"versionType": "git"
},
{
"lessThan": "971b40e3ca1279ca4917889e0195d33b66d071a4",
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
"versionType": "git"
},
{
"lessThan": "828ff461c136b95d13b8d712c0a7a06a640e313a",
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
"versionType": "git"
},
{
"lessThan": "ae69f936e8ffed553d899ba4c02f8a7461a89e54",
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
"versionType": "git"
},
{
"lessThan": "4c593c62c1499665baebbb41b70e2c9b7e947b86",
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
"versionType": "git"
},
{
"lessThan": "f5bcf539484d2d604c2f2330e09487ea090b21c7",
"status": "affected",
"version": "b8511ccc75c033f6d54188ea4df7bf1e85778740",
"versionType": "git"
},
{
"status": "affected",
"version": "d20edc0bca5577bab38acb5b190619c922ddebf8",
"versionType": "git"
},
{
"status": "affected",
"version": "1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625",
"versionType": "git"
},
{
"status": "affected",
"version": "40300f986e47dbc8f1d02e5080385f5cf9f85f70",
"versionType": "git"
},
{
"status": "affected",
"version": "b5a4949897ebada8132d54c93208989482503103",
"versionType": "git"
},
{
"lessThan": "4.15",
"status": "affected",
"version": "4.14.170",
"versionType": "semver"
},
{
"lessThan": "4.20",
"status": "affected",
"version": "4.19.102",
"versionType": "semver"
},
{
"lessThan": "5.5",
"status": "affected",
"version": "5.4.18",
"versionType": "semver"
},
{
"lessThan": "5.6",
"status": "affected",
"version": "5.5.2",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/resctrl/rdtgroup.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.6"
},
{
"lessThan": "5.6",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.191",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.114",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.52",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.191",
"versionStartIncluding": "5.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.160",
"versionStartIncluding": "5.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.114",
"versionStartIncluding": "5.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.52",
"versionStartIncluding": "5.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2.6",
"versionStartIncluding": "5.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.3",
"versionStartIncluding": "5.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.14.170",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "4.19.102",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.5.2",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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. ]"
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:35:58.210Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/906b3044dbf7c38cc411f7cf457c811363161e3b"
},
{
"url": "https://git.kernel.org/stable/c/971b40e3ca1279ca4917889e0195d33b66d071a4"
},
{
"url": "https://git.kernel.org/stable/c/828ff461c136b95d13b8d712c0a7a06a640e313a"
},
{
"url": "https://git.kernel.org/stable/c/ae69f936e8ffed553d899ba4c02f8a7461a89e54"
},
{
"url": "https://git.kernel.org/stable/c/4c593c62c1499665baebbb41b70e2c9b7e947b86"
},
{
"url": "https://git.kernel.org/stable/c/f5bcf539484d2d604c2f2330e09487ea090b21c7"
}
],
"title": "fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-93100",
"datePublished": "2026-09-17T16:11:13.077Z",
"dateReserved": "2026-09-17T16:02:15.085Z",
"dateUpdated": "2026-10-30T12:35:58.210Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
Loading…
Loading…
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
Loading…
Loading…