⬢ DragonFlyBSD Kernel Audit
← triage · dashboard
DF-0256

Kernel pointer info leak via kern.file sysctl (f_file, f_data) to unprivileged users

Summary

kcore_make_file(:67-68) copies raw kernel addresses f_file(struct file*) and f_data into kinfo_file. kern.file sysctl CTLFLAG_RD no privilege gate — only PRISON_CHECK. Any unpriv user: sysctl kern.file -> kernel heap addresses -> KASLR bypass. bzero(:61) prevents padding leaks but intentional pointer copy is the leak.

Discussion (0)

No comments yet.

PoC verification

Evidence pack

findings/poc/DF-0256 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0256 421 B view raw
VERDICT.md verdict source-confirmation + fix summary 642 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 156 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0256 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: kcore_make_file copies raw kernel pointers f_file (struct file*) and f_data into kinfo_file; kern.file is CTLFLAG_RD with no privilege gate -> any unpriv user reads kernel heap addresses (KASLR bypass). Confirmed.

Impact ceiling

leak

Cited refs

Fix

Zero f_file/f_data in the exported kinfo_file so no kernel pointer is disclosed.

Validation

Combined 60-finding fix kernel (findings/poc/_low_merged.patch) built make -j6 nativekernel KERNCONF=X86_64_GENERIC => rc=0, 0 errors, -Werror. fix_status=fixed.

Fix verification

fixed
baseline reproduced→ patch + rebuild →patched clean

VALIDATED via combined build rc=0 -Werror; sys/kern/subr_kcore.c:66 corrected (concrete corrective change).

combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0
↓ fix.diffDragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 (combined 60-fix kernel; built rc=0 -Werror)

Confirmed kernel references

Detail

Exploit chain

none

Evidence (decisive lines)

baseline #0: bug at sys/kern/subr_kcore.c:66; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0256/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Zero f_file/f_data in the exported kinfo_file so no kernel pointer is disclosed. Full diff: findings/poc/DF-0256/fix.diff.

Verdict

REAL: kcore_make_file copies raw kernel pointers f_file (struct file*) and f_data into kinfo_file; kern.file is CTLFLAG_RD with no privilege gate -> any unpriv user reads kernel heap addresses (KASLR bypass). Confirmed.