# DF-3745 — Connector/encoder object-table walks dereference unvalidated VBIOS offsets and indices — OOB heap reads at connector init

**Severity**: Medium · **CWE**: CWE-125 Out-of-bounds Read · **File**: sys/dev/drm/radeon/radeon_atombios.c:537-548, 551-557, 654-656, 682-698, 732-740, 660-672, 772-803

## What this is
radeon_get_atom_connector_info_from_object_table() (the DCE4+ connector path) dereferences a web of unvalidated BIOS values: (1) table bases from u16 offsets usStateArrayOffset/usClockInfoArrayOffset/usNonClockInfoArrayOffset/usDisplayPathTableOffset/usConnectorObjectTableOffset/usEncoderObjectTableOffset/usRouterObjectTableOffset (:537-548); (2) the display-path walk accumulates attacker u16 usSize values (:551-557) — two 0x8000 sizes put the record pointer 64 KiB out; (3) per-object usRecordOffset/usSrcDstTableOffset u16 offsets dereferenced immediately (:654-656, :685-698); (4) router src/dst: enum_id runs to *num_dst_objs (u8<=255) then indexes ucMuxState[enum_id] though ucMuxState is UCHAR[2] (atombios.h:4380-4395) — up to 253 B OOB (:732/:740); (5) record chains stepped by ucRecordSize with no image-end bound (:660-672, :772-803). All of this reads past the rdev->bios heap image at boot/attach (values feed connector config; distinct surface from the power-table indices of DF-1200). Harness on guest demonstrates each sub-case. Kernel path unreachable on this guest.

## Reproduce
```
./build.sh    # cc -O1 -g -Wall -o <bin> harness_objtable.c   (DragonFly guest, cc 8.3)
./run.sh      # expected: path walk goes OOB at path 1 (offset 0x6666 > 4096-byte image); record offset 0xFFF0 deref; enum_id=255 vs ucMuxState[2]; chain walks past image end; exit_code=0
```
The harness replicates the kernel parse arithmetic VERBATIM (cited path:line) against a
synthetic crafted-VBIOS buffer with canary-guarded destinations.

## Guest / environment
Guest has NO AMD/radeon GPU (virtio-only); /boot/kernel/radeon.ko exists (code shipped in the default install) but cannot attach, so the kernel code path is unreachable at runtime on this guest. Evidence is source-level certainty (path:line traced) plus a verbatim-arithmetic userland harness compiled and executed on the guest (build.log/run.log).
See env.txt (uname, cc, kldstat, /boot/kernel/radeon.ko presence).

## Fix
validate every BIOS offset/size against the image length before use (needs the bios_size plumbing of DF-3744) — see fix.diff (authored after verification; never applied to sys/).