[CVE-2024-57798][MODERATE 7.0] drm/dp_mst: Ensure mst_primary pointer is valid in drm_dp_mst_handle_up_req() [ Upstream

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

CVE: CVE-2024-57798
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/dp_mst: Ensure mst_primary pointer is valid in drm_dp_mst_handle_up_req() [ Upstream
Commit: f61b2e5e7821f868d6afc22382a66a30ee780ba0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f61b2e5e7821f868d6afc22382a66a30ee780ba0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2024-57798
Analysis date: Wed, 09 Sep 2026 02:25:31 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2024-57798 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2024-57798

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2024-57798	MODERATE	https://www.kernelcve.org/list/?q=CVE-2024-57798 CHECK WITH IMPACT FROM ORIG NN LOW	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-362;*CWE-416;**CWE-476;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in DRM DisplayPort MST handling can occur when drm_dp_mst_handle_up_req processes an MST up request while another thread disables the MST topology and frees mst_primary. This can leave the request handler using a NULL or freed mst_primary pointer during ACK handling or connection status processing, causing at least a kernel crash. For the CVSS the PR:L is used in the paranoid score because a local user or local display control process may be able to influence MST topology changes, while the primary hardware trigger depends on DisplayPort MST behavior rather than a network service. The issue is not network reachable and requires a local display path or a malicious or unstable DP MST device. Impact is at least denial of service via kernel crash. Because the pointer can be freed while still used by another thread, this is a UAF candidate and worst case impact may include confidentiality or integrity impact, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) 	MAYBE	LOCK INIT UAF LOG HARDWARE KPANIC 	-	-	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

No floor or cap changed the conservative score. No floor or cap changed the paranoid score.

2. Signal breakdown

Conservative signals:

* +2 Real UAF / active lifetime violation. The commit directly states that `mst_primary` can be freed by `drm_dp_mst_topology_mgr_set_mst(false)` while `drm_dp_mst_handle_up_req()` still uses it.
* +1 Reliable kernel crash / strong DoS. The stale pointer can cause NULL dereference or use-after-free in the kernel display stack.
* +1 Firmware/device-mediated external influence. The vulnerable path handles DisplayPort MST up request messages, which can be influenced by a connected MST device or hub.
* 0 Hard race penalty not awarded. The bug is a race, but the supplied evidence does not prove a one-shot or extremely hard timing window.

Paranoid additional signal:

* +1 Structured stale-object exploitation concern. `mst_primary` is an active DRM MST branch object, not a fixed stale buffer, and stale use reaches ACK handling and `link_address_sent` processing. This is still not a controlled reclaim or arbitrary write primitive, so only a limited paranoid point is awarded.

Important non-awarded signals:

* Controlled reclaim not demonstrated.
* Arbitrary read or write not demonstrated.
* Callback or function-pointer control not demonstrated.
* Concrete repeated release/refcount mutation on the same dangling reference not established.
* Extra Availability not awarded because the crash/DoS is already counted once.
* C/I impact not awarded conservatively because the patch supports NULL deref/UAF and crash, not a concrete disclosure or integrity primitive.
* Strong LPE leverage +2 not awarded because no attacker-shaped replacement object, refcount takeover, or directed corruption is shown.
* Remote network reachability not established.

Repeated-release/refcount checks:

* First release can end lifetime: yes, topology teardown can free `mst_primary`.
* Exact same reference survives: yes, `drm_dp_mst_handle_up_req()` can keep using the old `mgr->mst_primary` value without a reference.
* Second operation is a real lifetime/refcount mutation: no. The stale use is dereference/use in ACK and status processing, not a second `put` or `release`.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage awarded: no.
* FLOOR 5 from repeated release/refcount: no.

3. Reachability analysis

The vulnerable event requires concurrent MST up request handling and MST topology teardown. A malicious or unstable DisplayPort MST device can plausibly influence the up request side, while topology disable can be caused by display hotplug, unplug, mode management, driver teardown, or display stack activity.

Ordinary below-host-admin reachability is not fully established from the supplied patch. A logged-in graphical user, compositor, DRM master, or display service may influence display topology in real deployments, but the complete vulnerable operation is not proven to be reachable by an ordinary unprivileged user. Therefore `HostAdminRequired=UNKNOWN`, not `NO`.

This is not namespace-scoped. Network namespaces or container capabilities are not relevant to this DRM/KMS path.

Prior setup may include a system with DisplayPort MST enabled and an MST-capable monitor or hub. This is hardware-specific, but common GPU/display hardware is not treated as rare hardware by itself. The issue is not network reachable.

Race repeatability is uncertain. The race involves two concurrent threads, but the evidence does not prove that the timing is extremely narrow or practically one-shot.

4. Primitive and severity interpretation

The exact primitive is a race-driven stale pointer use of `mst_primary`. The object is an active structured DRM MST branch object. It is not fixed stale storage.

The stale use is broader than cleanup-only behavior. The stale object can be passed to `drm_dp_send_up_ack_reply()` and later used for connection status processing through `mst_primary->link_address_sent`.

This is `CLASS_B`: a real kernel lifetime/UAF primitive requiring exploitation-leverage analysis. It is not `CLASS_A` because controlled reclaim, arbitrary kernel read/write, callback control, refcount takeover, or demonstrated LPE is not established.

The demonstrated consequence is kernel crash / DoS through NULL dereference or use-after-free. The speculative consequence is limited C/I impact if stale structured object reuse could be made useful, but that is not proven by the patch.

`ImportantCandidate=YES` because this is an active structured UAF in DRM MST request processing with unresolved exploitation leverage beyond a simple NULL dereference. `AutoDowngradeAllowed=NO` because automatically closing it as ordinary crash-only Moderate would discard a concrete active-object UAF that still needs manual review.

Likely operational severity is Actionable Moderate, with Strong Important candidacy depending on whether a real below-host-admin trigger and useful post-free object reuse can be established.

5. One-sentence report phrase

A race in DRM DisplayPort MST up request handling can leave `drm_dp_mst_handle_up_req()` using a NULL or freed `mst_primary` branch object after concurrent topology teardown, causing at least a local or device-mediated kernel crash and requiring manual review for UAF exploitability.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: concrete active-object UAF is established, and the stale object is used in normal MST request processing rather than only in a trivial cleanup fault path.

7. Call-site confidence

Call-site confidence: high

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

Patch: drm/dp_mst: Ensure mst_primary pointer is valid in drm_dp_mst_handle_up_req() [ Upstream
Commit: f61b2e5e7821f868d6afc22382a66a30ee780ba0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f61b2e5e7821f868d6afc22382a66a30ee780ba0

Changed files:
  drivers/gpu/drm/display/drm_dp_mst_topology.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=f61b2e5e7821f868d6afc22382a66a30ee780ba0

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

The original Linux kernel CVE announcement for CVE-2024-57798 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2024-57798

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:P/AC:H/PR:N/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: 4
  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: YES
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).