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CVE-2026-93100

fs/resctrl: Prevent use-after-free in rdtgroup_kn_put()

Products / packages Linux

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Severity and exploitation

Not in CISA KEVNo CVSS score

KEV coverage does not rule out exploitation.

KEV checked 14/11/2026, 21:10:34 UTC

Severity

unknown

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Source guidance available

Review the recorded instructions. Guidance may be a workaround rather than a fixed version.

What this means

In the Linux kernel, the following vulnerability has been resolved:

Source excerpt · Linux

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

Linux · Linux

Linux

14 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

b8511ccc75c033f6d54188ea4df7bf1e85778740 → before 906b3044dbf7c38cc411f7cf457c811363161e3b

git versions

b8511ccc75c033f6d54188ea4df7bf1e85778740 → before 971b40e3ca1279ca4917889e0195d33b66d071a4

git versions

b8511ccc75c033f6d54188ea4df7bf1e85778740 → before 828ff461c136b95d13b8d712c0a7a06a640e313a

git versions

b8511ccc75c033f6d54188ea4df7bf1e85778740 → before ae69f936e8ffed553d899ba4c02f8a7461a89e54

git versions

b8511ccc75c033f6d54188ea4df7bf1e85778740 → before 4c593c62c1499665baebbb41b70e2c9b7e947b86

git versions

b8511ccc75c033f6d54188ea4df7bf1e85778740 → before f5bcf539484d2d604c2f2330e09487ea090b21c7

git versions

d20edc0bca5577bab38acb5b190619c922ddebf8

git versions

1b006f8cbde9f3dabdfafe2ff7aa9f831ed5b625

git versions

40300f986e47dbc8f1d02e5080385f5cf9f85f70

git versions

b5a4949897ebada8132d54c93208989482503103

git versions

4.14.170 → before 4.15

semver versions

4.19.102 → before 4.20

semver versions

5.4.18 → before 5.5

semver versions

5.5.2 → before 5.6

semver versions

unaffected

unknown

Other versions: unaffected

Linux · Linux

Linux

8 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

5.6

unaffected

0 → before 5.6

semver versions

6.1.191 → through 6.1.*

semver versions

6.6.160 → through 6.6.*

semver versions

6.12.114 → through 6.12.*

semver versions

6.18.52 → through 6.18.*

semver versions

7.2.6 → through 7.2.*

semver versions

7.3 → through *

original_commit_for_fix versions

unknown

Other versions: affected

Automatic dependency matching is unavailable for this record. Use the product evidence and publisher’s instructions to check your installation.

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

Remove resource group, which in turn drops its kernfs reference, after kernfs protection is restored.

Linux guidance ↗

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher 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. ]

References

6 sources
git.kernel.org/stable/c/906b3044dbf7c38cc411f7cf457c811363161e3b
Source referenceLinux
git.kernel.org/stable/c/971b40e3ca1279ca4917889e0195d33b66d071a4
Source referenceLinux
git.kernel.org/stable/c/828ff461c136b95d13b8d712c0a7a06a640e313a
Source referenceLinux
git.kernel.org/stable/c/ae69f936e8ffed553d899ba4c02f8a7461a89e54
Source referenceLinux
git.kernel.org/stable/c/4c593c62c1499665baebbb41b70e2c9b7e947b86
Source referenceLinux
git.kernel.org/stable/c/f5bcf539484d2d604c2f2330e09487ea090b21c7
Source referenceLinux

Inside the record

Evidence available

Package identity · not supplied
Version evidence
Remediation guidance · not supplied
Weakness classification · not supplied
Additional publishers · not supplied

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-93100

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Environment requirements

These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.

Linux · platform conditions

Any condition may hold

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.6

Before: 6.1.191

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.6

Before: 6.6.160

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.6

Before: 6.12.114

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.6

Before: 6.18.52

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.6

Before: 7.2.6

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.6

Before: 7.3

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 4.14.170

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 4.19.102

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.4.18

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.5.2

Applicability preview
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Contributing organizations · 1
Linux

Assigning organization

2026-10-30

Timeline

All times UTC

  1. Advisory published

    Publication date supplied by the source.

  2. Source updated

    Latest modification date supplied by the source.

  3. Last imported by cve.new

    Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes
No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.