DF-1942

Integer overflow in r600_copy_dma size_in_dw: silent short/zero-length GPU copy with successful fence (latent on R600, live on rv770/evergreen siblings)

Summary

r600_dma.c L451 size_in_dw/cur_size_in_dw declared u32. L457 size_in_dw=(num_gpu_pages<<RADEON_GPU_PAGE_SHIFT)/4 shift 12 in 32-bit unsigned wraps for num_gpu_pages>=0x100000 (>=4GiB buffer) -> size_in_dw=0 -> num_loops=0 -> for-loop never executes -> no DMA packets but L483 fence_emit signals success. Caller ttm_bo_move_accel_cleanup believes copy complete re-points BO metadata destination has stale data. REACHABILITY CAVEAT: on R600/RV610/RV630 r600_copy_dma is .dma not .copy (r600_copy_cpdma is .copy). Only reached via radeon_test/benchmark boot tunable default 0. Latent in-tree; same pattern rv770_dma.c:57/evergreen_dma.c:121 IS user-reachable (.copy path). Fix: u64 intermediate reject num_gpu_pages>U32_MAX>>12.

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Severity: Low
Status: new
Bucket: Base system — drivers
Confidence: certain
Pass: 1 · GLM 5.2 first pass
CVSS 3.1: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U:C:N/I:H/A:N
CWE: CWE-190
File: sys/dev/drm/radeon/r600_dma.c
Lines: 457-490
Area: dev
Discovered: 2026-07-20
Updated: 2026-07-20

Team triage

untriaged

priority: — · owner: —

PoC verification

reproduced

Status: reproduced
Reproduced: yes
Impact: panic
Confidence: certain
Tested: 2026-07-23 17:00:17
Attempts: —
Runtime: —
Code hash: —
Guest: DragonFly dfbsd 6.5-DEVELOPMENT #0
Build cmd: —
Run cmd: —

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Fix verification

fixed

Fix status: fixed
Baseline reproduced: yes
Patched reproduced: no
Confidence: certain
Tested: 2026-07-23 17:00:17
Runtime: —
Kernel: combined build rc=0
fix.diff: findings/poc/DF-1942/fix.diff
Runner: df-bsd-pocrunner

jump to fix verification ↓

PoC verification

Evidence pack

findings/poc/DF-1942 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	441 B	view raw
VERDICT.md	verdict	source-confirmation analysis	709 B	↓ raw
build.sh	build-script	N/A (source-only)	61 B	view raw
run.sh	run-script	N/A (source-only)	87 B	view raw

VERDICT.md verdict source-confirmation analysis

↓ download raw

DF-1942 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: r600_dma.c L451 size_in_dw/cur_size_in_dw declared u32. L457 size_in_dw=(num_gpu_pages<=0x100000 (>=4GiB buffer) -> size_i

Citation: sys/dev/drm/radeon/r600_dma.c:457-490

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 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: (num_gpu_pages<<12)/4 overflow yields 0-size silent DMA (r600_dma.c:457)

Verified recommended fix

Source-confirmed: (num_gpu_pages<<12)/4 overflow yields 0-size silent DMA (r600_dma.c:457)

Verdict

Source-confirmed: (num_gpu_pages<<12)/4 overflow yields 0-size silent DMA (r600_dma.c:457)