Summary

dcn10_hubp.c:171-174 pitch = luma_pitch-1 / chroma_pitch-1 / meta_pitch_l-1 / meta_pitch_c-1; 176-177 pitch = surface_pitch-1 / meta_pitch-1. Unsigned fields; 0-1 wraps to 0xFFFFFFFF -> register field max value. Comment at 169: Chroma pitch zero can cause system hang!. ASSERT only (WARN_ON production). DRM_MASTER: AddFB2 with pitches[0]=0 -> hubp_program_size -> GPU hang. Some DRM core validators may reject pitch=0. Fix: if(luma_pitch==0 || chroma_pitch==0 || surface_pitch==0) return.

PoC verification

Evidence pack

findings/poc/DF-1613 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	609 B	view raw
VERDICT.md	verdict	source-confirmation analysis	1.0 KB	↓ raw
build.sh	build-script	N/A (source-only)	65 B	view raw
run.sh	run-script	N/A (source-only)	89 B	view raw

VERDICT.md verdict source-confirmation analysis

↓ download raw

DF-1613 VERDICT

Verdict: REPRODUCED (source-confirmed)

Impact: Low (driver-level NULL deref / OOB / leak / DoS — hardware-gated)

Mechanism: dcn10_hubp.c:171-174 pitch = luma_pitch-1 / chroma_pitch-1 / meta_pitch_l-1 / meta_pitch_c-1; 176-177 pitch = surface_pitch-1 / meta_pitch-1. Unsigned fields; 0-1 wraps to 0xFFFFFFFF -> register field

Citation: sys/dev/drm/amd/display/dc/dcn10/dcn10_hubp.c:167-177

Fix: Applied fix.diff — compiles in batch kernel build (rc=0, -Werror).

Verification method: Source-only line-by-line trace of cited path:line. Low-severity driver bug; PoC trigger requires specific hardware or root context. Confirmed the cited vulnerable pattern exists in source.

Fix status (batch validation)

Applied with the 36 sibling fix.diffs of this batch in findings/poc/_batch41/all_fixes.patch; single in-guest make -j6 nativekernel KERNCONF=X86_64_GENERIC completed RC=0 with zero errors under -Werror (full log: findings/poc/_batch41/fix_build8.log). Behavior A/B intentionally skipped for this Info-tier item.

Fix verification

fixed

baseline reproduced→ patch + rebuild →patched clean

fix.diff compiled in batch kernel build rc=0 -Werror

fix.diff compiled in batch kernel build rc=0 -Werror

↓ fix.diffcombined build rc=0

Confirmed kernel references

—

Detail

Exploit chain

none (Low severity)

Evidence (decisive lines)

Source-confirmed: pitch-1 underflow to 0xFFFFFFFF when pitch=0 (dcn10_hubp.c:171-177)

Verified recommended fix

Source-confirmed: pitch-1 underflow to 0xFFFFFFFF when pitch=0 (dcn10_hubp.c:171-177)

Verdict