DF-4934

dig_encoder_sel_to_atom computes a 7-case DIGx_SEL mapping then discards it with literal 'return 0' (v2; DF-2030 dce110 sibling; upstream-intended dead code)

Summary

The switch computes the mapping then returns literal 0 - upstream codified always-0 as intended (post-DCE80 manual DIG_FE). The dead switch invites a behavior-changing cleanup. Info hardening.

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Severity: Info
Status: new
Bucket: Base system — drivers
Confidence: certain
Pass: 2 · GLM 5.3 second pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:N
CWE: CWE-563
File: sys/dev/drm/amd/display/dc/bios/dce112/command_table_helper2_dce112.c
Lines: 151-187
Area: dev
Discovered: 2026-09-25
Updated: 2026-09-25

Team triage

untriaged

priority: — · owner: —

PoC verification

untested

Status: untested
Reproduced: no
Impact: none
Confidence: certain
Tested: 2026-09-25 06:49:03
Attempts: 0
Runtime: —
Code hash: —
Guest: —
Build cmd: —
Run cmd: —

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Fix verification

not_testable

Fix status: not_testable
Baseline reproduced: —
Patched reproduced: —
Confidence: certain
Tested: 2026-09-25 06:49:03
Runtime: —
Kernel: per-fix-DF-4934
fix.diff: findings/poc/DF-4934/fix.diff
Runner: df-bsd-reviewer

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PoC verification

Evidence pack

findings/poc/DF-4934 · 1 files

File	Type	Description	Size
verdict.json	file		852 B	view raw

Fix verification

not_testable

per-fix-DF-4934

Confirmed kernel references

Detail

Exploit chain

none - intended encoding, static observation only

Evidence (decisive lines)

findings/poc/DF-4934/ (this verdict)

Verdict

Dead-code trap (Info): the full 7-case ENGINE_ID_DIG{A..G} switch computes ATOM_TRANSMITTER_V6__DIG_SEL then discards it with literal return 0 - the live v2 consumer always programs digfe_sel=0, which upstream has codified as INTENDED (post-DCE80 DIG_FE is programmed manually by connect_dig_be_to_fe). The dead switch invites a behavior-changing cleanup. DF-2030 is the dce110-v1 sibling. Delete-the-dead-switch upstream fix.