Summary

solo.c:769 ess_dmasetup cnt param u_int16_t; caller esschan_trigger:600 passes sndbuf_getsize() u_int32_t max 65536. 772 dmasz=cnt truncates 65536->0. 779 port_wr(vc,0x4,cnt-1,2)=0xFFFF correct DMA but driver notion=0. ess_dmapos:813 while(p>dmasz[ch-1]||...) becomes p>0 always true -> spin 1000*DELAY(10)=10ms under ess_lock + kprintf spam. 818 return dmasz-p = 0-p negative int -> esschan_getptr u32 huge. framework delta overcounts -> sndbuf_acquire marks uninitialized heap as ready -> read() leaks ~64KB kernel heap. DMA buffer bus_dmamem_alloc no BUS_DMA_ZERO. Trigger: hint.snd_solo.0.buffersize=65536 + /dev/dsp read. Fix: widen cnt to u32 + cap dmasz at 0xffff or special-case 64KB.

PoC verification

Evidence pack

findings/poc/DF-1638 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	887 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-1638 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: solo.c:769 ess_dmasetup cnt param u_int16_t; caller esschan_trigger:600 passes sndbuf_getsize() u_int32_t max 65536. 772 dmasz=cnt truncates 65536->0. 779 port_wr(vc,0x4,cnt-1,2)=0xFFFF correct DMA bu

Citation: sys/dev/sound/pci/solo.c:769-818

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: u_int16_t cnt truncation of 65536 buffer size to 0 (solo.c:769,600)

Verified recommended fix

Source-confirmed: u_int16_t cnt truncation of 65536 buffer size to 0 (solo.c:769,600)

Verdict