⬢ DragonFlyBSD Kernel Audit
← triage · dashboard
DF-0261

act_ofs copied from user input without validation against cmd_len -> heap OOB read

Summary

ipfw_check_ioc_rule(:5311) never validates act_ofs<=cmd_len. rule->act_ofs raw copy from user(:4515). ACTION_PTR(f)=cmd+act_ofs(ip_fw2.h:442). check-state(:4207) derefs cmd->opcode at OOB offset -> panic on unknown opcode(:4367). Root-only: IP_FW_ADD with act_ofs>cmd_len + check-state hit.

Discussion (0)

No comments yet.

PoC verification

Evidence pack

findings/poc/DF-0261 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0261 442 B view raw
VERDICT.md verdict source-confirmation + fix summary 618 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 160 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0261 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: ipfw_check_ioc_rule never validates act_ofs<=cmd_len; rule->act_ofs is copied raw from user (line 4515) and ACTION_PTR(f)=cmd+act_ofs, so check-state derefs an OOB opcode -> panic. Root-only (IP_FW_ADD).

Impact ceiling

none

Cited refs

Fix

Reject the rule in ipfw_check_ioc_rule when act_ofs > cmd_len.

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/net/ipfw/ip_fw2.c:5311 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/net/ipfw/ip_fw2.c:5311; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0261/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Reject the rule in ipfw_check_ioc_rule when act_ofs > cmd_len. Full diff: findings/poc/DF-0261/fix.diff.

Verdict

REAL: ipfw_check_ioc_rule never validates act_ofs<=cmd_len; rule->act_ofs is copied raw from user (line 4515) and ACTION_PTR(f)=cmd+act_ofs, so check-state derefs an OOB opcode -> panic. Root-only (IP_FW_ADD).