Summary

acpi_battery_clean_str L321-334: for(i=0;i<len&&*str!=0;i++,str++) increments str to str+len when no NUL in len bytes. Post-loop if(i==len)*str=0 writes NUL at str+len one byte past callers buffer. For oeminfo (last field struct acpi_bif) writes past struct past union acpi_battery_ioctl_arg past kmalloc ioctl buffer. Reachable via ACPIIO_BATT_GET_BIF ioctl when SMBus battery returns 32-byte string field without NUL: acpi_smbus_read_multi_1 acpi_smbat.c:320 val=(BCNT&0x1f)+1 can be exactly 32 writes all 32 bytes no NUL; acpi_smbat_get_bif memcpy L488; acpi_battery_clean_str called L408-415. Control-method battery safe (acpi_PkgStr forces NUL within 32). Local unpriv user /dev/acpi. kmalloc(164) slab rounds to 192/256 padding benign in practice but genuine memory-safety defect. Fix: write NUL at str[len-1] when i==len (truncate last char).

PoC verification

Evidence pack

findings/poc/DF-1928 · 4 files

File	Type	Description	Size
fix.diff	suggested-fix	git-apply-able fix for the cited bug	292 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-1928 VERDICT

Verdict: REPRODUCED (source-confirmed)

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

Mechanism: acpi_battery_clean_str L321-334: for(i=0;i<len&&str!=0;i++,str++) increments str to str+len when no NUL in len bytes. Post-loop if(i==len)str=0 writes NUL at str+len one byte past callers buffer. Fo

Citation: sys/dev/acpica/acpi_battery.c:326-333

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: off-by-one NUL write past buffer in clean_str (acpi_battery.c:326-333)

Verified recommended fix

Source-confirmed: off-by-one NUL write past buffer in clean_str (acpi_battery.c:326-333)

Verdict