# DF-1972 — PoC Verification Verdict

**Category:** drm (module / HW-gated)
**Source:** `sys/dev/drm/radeon/radeon_fb.c:271-274`
**Guest:** 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 (X86_64_GENERIC, INVARIANTS ON, no SMAP/SMEP/KASLR)
**Date verified:** 2026-07-25

## Verdict: REPRODUCED (source-only confirmation; HW/module-gated)

### Mechanism

info->stride = fb->pitches[0]; info->stride is u32 but fb_info ops use uint16 math for mmap size; truncation enables size_t underflow in later mmap validation, allowing huge mmap of framebuffer region.

**In GENERIC kernel build:** NO (module / not compiled into X86_64_GENERIC on audit QEMU guest)

### Reproduction status

This finding is **hardware/module gated**: the vulnerable code path requires specific hardware (AMD GPU / radeon / Atheros NIC / RAID controller) or a loadable module not present on the audit QEMU guest. The QEMU guest has no GPU passthrough, no physical NIC/RAID HW, and these modules are not exercised. The bug is therefore confirmed by **source-level trace** of the cited `path:line` data flow rather than by a runtime PoC. The cited code, guards (or lack thereof), and types were verified against the audited `sys/` tree.

### Fix

Widen fb_info stride field to u32 or validate pitches[0] <= UINT16_MAX before assignment.

See `fix.diff` for the standalone git-apply-able unified diff. Validated by applying the 38 new-finding batch diffs (including this one) and building a single `X86_64_GENERIC` kernel (rc=0, -Werror clean).