Bug 2513201 (CVE-2026-68235)

Summary: CVE-2026-68235 kernel: drm/amd/display: dce100: skip non-DP stream encoders for DP MST
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's AMD display (drm/amd/display) driver. This vulnerability occurs when handling DisplayPort Multi-Stream Transport (MST) for DCE8-class ASICs, where the system may incorrectly assign an analog encoder that lacks necessary DisplayPort functions. This misassignment can lead to a null pointer dereference, causing the kernel to crash. A local attacker could exploit this to trigger a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-08-10 12:24:37 UTC 
In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: dce100: skip non-DP stream encoders for DP MST

On DCE8-class ASICs (e.g. Bonaire), the resource pool contains digital
DIG stream encoders plus one analog DAC encoder. When assigning a stream
encoder for a second DisplayPort MST stream, if the preferred digital
encoder is already acquired, dce100_find_first_free_match_stream_enc_for_link()
falls back to the first free pool entry. That entry may be the analog
encoder, whose funcs table lacks DP hooks such as dp_set_stream_attribute.
The subsequent atomic commit then dereferences NULL function pointers in
link_set_dpms_on() and crashes.

Skip encoders without dp_set_stream_attribute when the stream uses a DP
signal (including MST). Use dc_is_dp_signal(stream->signal) for the MST
fallback path instead of checking only the link connector signal.

Tested on:
- GPU: AMD Radeon R7 260X (Bonaire / DCE8)
- Board: Supermicro C9X299-PG300
- Setup: DP MST daisy chain, hotplug second monitor or have it connected on boot
- Kernel: 7.1.3 (issue observed since 6.19)
- Result: kernel oops without patch; dual monitors stable with patch

(cherry picked from commit 28ec64943e3ee4d9b8d30cea61e380f1429953a8)