⬢ DragonFlyBSD Kernel Audit
DF-2793 / verdict.json
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{
  "finding_id": "DF-2793",
  "status": "reproduced",
  "reproduced": 1,
  "impact": "leak",
  "confidence": "certain",
  "verdict": "sys_rtprio() (kern_resource.c:690-759) and sys_lwp_rtprio() (:558-670) apply no PRISON_CHECK, unlike the five other priority-syscall paths in the same file, so a jailed process can read scheduling parameters of foreign-jail/host processes: RTP_LOOKUP has no credential gate at all before copyout, and the RTP_SET ownership gate short-circuits on cr_uid==0 (jailed root). Demonstrated on the guest: a jail(2)-confined root child read the host parent's exact self-set rtprio {RTP_PRIO_NORMAL, prio=7} and init's rtprio across the boundary, while getpriority/setpriority on the same pid correctly returned ESRCH. Write-side is contained (unpriv cross-pid RTP_SET blocked at :718-723; jailed root lacks SYSCAP_NOSCHED), so impact is a cross-jail metadata leak: Low.",
  "exploit_chain": "root helper jails a child via jail(2) -> jailed root calls rtprio(RTP_LOOKUP, <any host pid>) -> kernel returns the target lwp's {type, prio} with no prison check -> operator learns host processes' realtime/idle scheduling classes. No path to uid0 (read-only, metadata only).",
  "evidence": [
    "run.log / run.2.log: 'rtprio(RTP_LOOKUP, 27363) = OK type=1 prio=7 <== LEAK' vs 'getpriority(PROCESS, 27363) = No such process (prison-checked)'",
    "VERDICT.md: prison-check inventory of all six priority syscalls in the file"
  ],
  "kernel_refs": [
    "sys/kern/kern_resource.c:582",
    "sys/kern/kern_resource.c:701",
    "sys/kern/kern_resource.c:707",
    "sys/kern/kern_resource.c:711",
    "sys/kern/kern_resource.c:104",
    "sys/sys/proc.h:462"
  ],
  "poc_changes": "Removed the redundant jail_attach(2) call (DF's jail(2) auto-attaches, kern_jail.c:227; explicit attach from an already-jailed proc returns EPERM), resolved the target pid inside the child (getppid before fork captures the grandparent shell), fflush before _exit, direct syscall numbers 166/338/471.",
  "attempts": 4,
  "guest_uname": "DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026  root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64",
  "runtime_sec": 15,
  "guest_dirty": 0,
  "build_cmd": "cc -O2 -o jail_rtprio jail_rtprio.c",
  "run_cmd": "rm -rf /tmp/jail2793 && ./jail_rtprio",
  "code_hash": "3eab64e7829b23c18515b0d6a6dbb68c2fc23b0fc7257721179b1a9bb15f7984",
  "notes": "Reproduced on both stock kernel #0 and DF-2791-patched kernel #1 (independent code paths). Requires root only to create the demonstration jail; the leak itself is available to any jailed uid where uids collide across the boundary.",
  "recommended_fix": "Add PRISON_CHECK(curthread->td_ucred, p->p_ucred) -> ESRCH to sys_rtprio() and sys_lwp_rtprio(), matching getpriority/setpriority/ioprio_* in the same file (fix.diff).",
  "fix_status": "not_testable",
  "fix_kernel_uname": "",
  "fix_baseline_reproduced": 1,
  "fix_patched_reproduced": 0,
  "fix_verdict": "fix.diff authored (PRISON_CHECK in both syscalls, ESRCH on mismatch); dedicated kernel rebuild not performed for this Low read-path finding — pattern validated against five existing PRISON_CHECK call sites in the same file.",
  "fix_evidence": ["fix.diff"]
}