# VERDICT -- DF-1385

## Verdict: INCONCLUSIVE at runtime; source bug CONFIRMED; fix COMPILE-VALIDATED

**Citations confirmed:**
  - sys/dev/drm/radeon/cypress_dpm.c:1052
  - sys/dev/drm/radeon/cypress_dpm.c:1081
  - sys/dev/drm/radeon/cypress_dpm.c:1060

### Is the bug real? -- YES (source trace)

cypress_initialize_mc_reg_table() calls radeon_atom_get_mclk_range_table() which
    returns num_entries from VBIOS usModuleSize (u8 0-255, no clamp).
cypress_retrieve_ac_timing_for_all_ranges() :1052 loops `i < num_entries` writing
    mc_reg_table_entry[i] which is fixed at MAX_AC_TIMING_ENTRIES=16.
num_entries>16 overflows the array into the eg_pi softc. btc_dpm.c:1995 has the
    `if (table->num_entries > MAX_AC_TIMING_ENTRIES)` check; cypress does not.

### Can it be reproduced on this guest? -- NO (hardware-gated)

No AMD GPU in PCI list (only QEMU stdvga 0x11111234); radeon.ko not loaded.

The radeon driver is a loadable module only (NOT in `X86_64_GENERIC`), is not loaded, and cannot be `kldload`'d by an unprivileged user (kldload is root-only). Even loaded, it would not attach without the hardware.
Therefore the vulnerable code is unreachable at runtime here. Because the sinks are device-integrated parsers / DRM ioctls / DMA-supplied indices / hardware-dependent paths, no userspace harness on this guest can exercise them. This is the documented valid hard-blocker "unreachable at runtime + no feasible harness"; the bug is a real latent defect with the live trigger conditions noted above.

### No escalation chain (and why that is correct here)
There is no memory-corruption primitive to escalate on this guest: the corruption sinks live entirely inside the not-attached driver behind hardware that is absent. The escalation work the audit expects (slab groom -> victim -> uid0) presupposes a reachable write primitive; here there is none on the guest. The deliverable is therefore the confirmed root-cause + a compile-validated fix.

### Fix (fix.diff) -- authored and COMPILE-VALIDATED
Added the missing `if (range_table.num_entries > MAX_AC_TIMING_ENTRIES) clamp`
in cypress_initialize_mc_reg_table(), mirroring btc_dpm.c:1995. (matches
finding proposal.)

The fix was applied to in-guest `/usr/src` (all hunks applied cleanly) and the
module was rebuilt with the kernel's `-Werror` flags: `cd /usr/src/sys/dev/drm/radeon && KERNCONF=X86_64_GENERIC SYSDIR=/usr/src/sys make -m /usr/src/share/mk` => rc=0 (see `build_fix.log`). No warnings or errors in the patched translation unit. The runtime before/after of the bug cannot be tested on this guest (no hardware), so fix_status is `not_testable` (diff applies + compiles; code path traced closed).

### Why not `not_reproduced` (false-positive)?
This is NOT a false positive. The cited `sys/` code is genuinely missing the guard / has the overflow / has the unclamped loop -- verified by reading the source. It is a real bug that is simply out of reach of this particular (driverless) QEMU guest.