CVE-2026-93100
Received
Received - Intake
BaseFortify
Vulnerability report for CVE-2026-93100, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-17
Last updated on: 2026-09-17
Assigner: kernel.org
Description
Description
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. ]
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Linux | Linux | b8511ccc75c033f6d54188ea4df7bf1e85778740 |
| Linux | Linux | b8511ccc75c033f6d54188ea4df7bf1e85778740 |
| Linux | Linux | b8511ccc75c033f6d54188ea4df7bf1e85778740 |
| Linux | Linux | d20edc0bca5577bab38acb5b190619c922ddebf8 |
| Linux | Linux | 1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625 |
| Linux | Linux | 40300f986e47dbc8f1d02e5080385f5cf9f85f70 |
| Linux | Linux | b5a4949897ebada8132d54c93208989482503103 |
| Linux | Linux | 4.14.170 |
| Linux | Linux | 4.19.102 |
| Linux | Linux | 5.4.18 |
| Linux | Linux | 5.5.2 |
| Linux | Linux | 5.6 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
