{
  "finding_id": "DF-4044",
  "status": "inconclusive",
  "reproduced": 0,
  "impact": "none",
  "confidence": "certain",
  "verdict": "Source-certain NULL write: on an unexpected reselection (untagged_srbs[t][l]==NULL and disc_count==0, amd.c:1834-1836) amd_Reselect leaves amd->active_srb NULL after queueing the ABORT (:1843 skipped). A hostile target that ignores ATN and clocks a MSG_DISCONNECT byte in MSG IN reaches amdparsemsg case MSG_DISCONNECT (amd.c:1217) which writes amd->active_srb->SRBState (:1218) \u2014 a NULL-page write fault in amd_intr context => kernel panic. The Q_TAG case guards active_srb!=NULL (:1229) and amdhandlemsgreject guards srb!=NULL (:1475); the DISCONNECT arm is the unguarded hole. Verified with a child process taking SIGSEGV on the exact store (run.log DF-4044). Hostile-target gated -> runtime inconclusive on this guest, source certain.",
  "exploit_chain": "hostile target: reselect an idle target/lun (active_srb=NULL, driver queues ABORT) -> send MSG_DISCONNECT byte -> amd_MsgInPhase0:1188 -> amdparsemsg:1218 NULL write => panic",
  "evidence": "run.log section DF-4044 (child signal 11 on active_srb->SRBState with NULL); VERDICT.md; fix_build.log; env.txt",
  "kernel_refs": [
    "sys/dev/disk/amd/amd.c:1218",
    "sys/dev/disk/amd/amd.c:1834",
    "sys/dev/disk/amd/amd.c:1836",
    "sys/dev/disk/amd/amd.c:1843",
    "sys/dev/disk/amd/amd.c:1229"
  ],
  "poc_changes": "Pass-2 reviewer authored demonstrator with a verbatim copy of the drivers amdsentmsg walk / handlemsgreject branch ladder / parsemsg DISCONNECT arm so branch selection is the kernels; fix.diff generated against the pristine file and compile-validated via full nativekernel rebuild on the guest (shared build with DF-4036..DF-4044, fix_build.log).",
  "attempts": 3,
  "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": 200,
  "guest_dirty": 0,
  "build_cmd": "./build.sh",
  "run_cmd": "./run.sh",
  "code_hash": "141db72d1d0fefdd08c49b0a88eb9fe244fa09f9e271000acd39d805a6ebdebd",
  "notes": "Hardware-gated (no AMD53c974 HBA on guest; hostile-SCSI-target threat model; amd(4) in GENERIC but never attaches). Kills: msgin_buf walk bounded (max idx 4), tag byte fits SRB_array[256], msgout shift fits, amdtimeout dead code (#if 0), EEPROM walks fit eepromBuf[128].",
  "recommended_fix": "NULL-guard active_srb in the MSG_DISCONNECT arm (skip the state store and disc_count bump; still complete the message)",
  "fix_status": "fixed",
  "fix_baseline_reproduced": 0,
  "fix_patched_reproduced": 0,
  "fix_kernel_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 (nativekernel X86_64_GENERIC rebuilt with all DF-4036..DF-4044 patches; 0 errors under -Werror; see fix_build.log)",
  "fix_verdict": "fixed (compile-validated): all nine patches applied together to the clean guest /usr/src copy (polaris10_smumgr.c md5 6f39bb32..->19a2b278.., amd.c f577a330..->54ce1518..), make -j4 nativekernel KERNCONF=X86_64_GENERIC completed RC=0 with 0 compile errors under -Werror; amd.o recompiled into the GENERIC kernel. Runtime re-test impossible on this guest (device absent). Sources restored to pristine and md5-verified after validation.",
  "fix_evidence": "findings/poc/DF-4044/fix.diff; findings/poc/DF-4044/fix_build.log (build banner + compile lines + 0 errors)"
}