[CVE-2026-68214][MODERATE 7.0] media: rtl2832: fix use-after-free in rtl2832_remove()

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-68214
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: media: rtl2832: fix use-after-free in rtl2832_remove()
Commit: 9acd5bbbe1df8e487e49488692c224496d4c9e16
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9acd5bbbe1df8e487e49488692c224496d4c9e16
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68214
Analysis date: Mon, 10 Aug 2026 12:57:16 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in rtl2832_remove() can reschedule i2c_gate_work after cancellation while device removal continues to kfree(dev), creating a delayed-work use-after-free that can crash the kernel and warrants manual review for possible memory-corruption impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-68214 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68214

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-68214	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in rtl2832_remove() can allow i2c_gate_work to be rescheduled after cancel_delayed_work_sync() has already returned. This can happen when an I2C transfer through the mux adapter is still in flight during device removal and rtl2832_deselect() schedules the delayed work again. The driver can then free the rtl2832 device state, leaving delayed work able to run later on freed memory. For the CVSS the PR:L reflects the paranoid local scenario where a local user or service can influence device teardown or hotplug related driver activity, while the realistic default path is often administrative or physical. The issue is not network reachable. Impact is at least local denial of service via kernel crash. Because this is a real use after free after kfree(dev), worst case impact may include memory corruption with possible privilege escalation and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	DANGER UAF HARDWARE LINUS SYZBOT  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Memory corruption, weak primitive: +1. The bug is a real UAF, but it is race-dependent and the patch does not show attacker-controlled reclaim, overwrite, type confusion, or arbitrary write.
* Real lifetime corruption: +1. `i2c_gate_work` can be rescheduled after cancellation and later run after `kfree(dev)`.
* Reliable kernel crash / strong DoS: +1. A delayed work item using freed driver state can plausibly cause a kernel crash.
* Hard or unreliable race / special timing required: -1. The trigger depends on an in-flight I2C transfer overlapping driver removal.
* Privileged/device teardown context: conservative interpretation lowers practical exploitability because removal/unbind/hotplug is usually administrative or physical.

Paranoid additional signals:

* Local unprivileged trigger concern: +1. In some deployments a local user may influence DVB device activity while teardown is triggered by hotplug, reset, or a management service.
* Weak LPE concern: +1. This is a delayed-work UAF, so callback/workqueue lifetime semantics make it more interesting than a plain NULL dereference, although no controlled reclaim primitive is shown.
* Privileged kernel/device-management lifetime corruption path: +1. The corruption occurs in driver teardown and asynchronous workqueue lifetime handling.

Race-UAF cap applies. Conservative score stays below Important. Paranoid score reaches Actionable Moderate but should not be treated as proven LPE.

## 3. Reachability analysis

The issue is local and device-dependent. It requires an RTL2832-related media/DVB device path and a race between an I2C mux transfer and device removal. Typical reliable triggering likely requires physical hotplug, driver unbind, device reset, or privileged device-management activity. It is not network reachable.

Namespaces do not obviously make this broadly reachable. A container or service with delegated device access could increase practical exposure, but ordinary containers usually do not control physical media device teardown. The path is not a broad default kernel interface like TCP, netfilter packet processing, io_uring, or page cache.

Call-site confidence: high. The commit message and diff directly show the cleanup order, delayed work cancellation, mux adapter removal, and final `kfree(dev)`.

## 4. Severity interpretation

This behaves like an actionable Moderate issue rather than an ordinary Low/Moderate cleanup bug because it is a real UAF after `kfree(dev)`. The realistic demonstrated impact is kernel crash / local DoS under a narrow race and hardware-specific teardown condition.

Theoretical privilege escalation is possible in the broad sense that kernel UAFs can sometimes be exploitable, and delayed work lifetime bugs deserve manual review. However, the patch does not demonstrate attacker-controlled reclaim, object replacement, write-after-free, type confusion, refcount takeover, or arbitrary write. Therefore it is not a strong Important candidate on the conservative evidence alone.

## 5. One-sentence report phrase

A race in rtl2832_remove() can reschedule i2c_gate_work after cancellation while device removal continues to kfree(dev), creating a delayed-work use-after-free that can crash the kernel and warrants manual review for possible memory-corruption impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: real kernel UAF in asynchronous delayed-work teardown. Even though the practical trigger is race-dependent and device-specific, the lifetime pattern is security-relevant enough to avoid auto-closure.

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UPSTREAM PATCH SUMMARY
======================================================================

Patch: media: rtl2832: fix use-after-free in rtl2832_remove()
Commit: 9acd5bbbe1df8e487e49488692c224496d4c9e16
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9acd5bbbe1df8e487e49488692c224496d4c9e16

Commit description:

cancel_delayed_work_sync() is called before i2c_mux_del_adapters()
in rtl2832_remove(). While the cancel waits for any running instance
of i2c_gate_work to finish, it does not prevent the timer from being
rescheduled by a concurrent thread.

During probe, the r820t_attach() call attempts I2C transfers through
the mux adapter. These transfers go through i2c_mux_master_xfer(),
which calls rtl2832_deselect() after the transfer completes,
rescheduling i2c_gate_work via schedule_delayed_work(). If this
transfer is still in flight when rtl2832_remove() runs,
rtl2832_deselect() can reschedule i2c_gate_work after it has been
cancelled, causing a use-after-free when kfree(dev) is called.

Fix this by calling i2c_mux_del_adapters() before
cancel_delayed_work_sync(). Once the mux adapter is unregistered, no
new I2C transfers can go through it, so rtl2832_deselect() can no
longer reschedule i2c_gate_work. The subsequent
cancel_delayed_work_sync() is then guaranteed to be final.

Fixes: cddcc40 ("[media] rtl2832: convert to use an explicit i2c mux core")
Cc: stable@vger.kernel.org
Reported-by: syzbot+019ced393ab913002b75@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=019ced393ab913002b75
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/media/dvb-frontends/rtl2832.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9acd5bbbe1df8e487e49488692c224496d4c9e16

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DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-68214 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68214

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 3
  Paranoid ActionableScore: 5

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE 7.0

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).