DF-4938

gfx sw_init partial-failure strands KIQ/MQD kernel BOs and mqd_backup allocations — teardown unreachable behind the IP-block status.sw gate

Summary

Allocation side has no unwind and the free side is gated behind a fully-successful sw_init - every bare return r in gfx_v8/v9 sw_init after kiq_init permanently pins ~9 BOs (VRAM/GTT) + 9 mqd_backup kmallocs until reboot, accumulating per probe retry. Info hygiene, hw-gated. Unwind-in-callers fix.

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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:L
CWE: CWE-404
File: sys/dev/drm/amd/amdgpu/amdgpu_gfx.c
Lines: 282-377
Area: dev
Discovered: 2026-09-25
Updated: 2026-09-25

Team triage

untriaged

priority: — · owner: —

PoC verification

untested

Status: untested
Reproduced: no
Impact: leak
Confidence: certain
Tested: 2026-09-25 07:02:11
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 07:02:11
Runtime: —
Kernel: per-fix-DF-4938
fix.diff: findings/poc/DF-4938/fix.diff
Runner: df-bsd-reviewer

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PoC verification

Evidence pack

findings/poc/DF-4938 · 1 files

File	Type	Description	Size
verdict.json	file		1.1 KB	view raw

Fix verification

not_testable

per-fix-DF-4938

Confirmed kernel references

Detail

Exploit chain

mid-probe failure (GTT/VRAM pressure) after kiq_init -> stranded BOs/kmallocs -> accumulate per retry

Evidence (decisive lines)

findings/poc/DF-4938/ (this verdict; static call-graph proof)

Verdict

Resource-exhaustion hygiene (Info, hw-gated): the gfx sw_init allocates persistent KIQ/MQD kernel BOs (KIQ EOP, KIQ MQD in VRAM, up to 8 compute MQDs in GTT) plus mqd_backup kmallocs with NO internal unwind, and the only teardown (sw_fini) is gated behind a fully-successful sw_init by the driver core - every bare return r in gfx_v8/v9 sw_init after kiq_init succeeds permanently pins ~9 BOs + 9 kmallocs until reboot, accumulating across probe retries. No unpriv trigger, no corruption. Unwind-in-callers fix (representative gfx_v9 diff).