# DF-1728 — Verdict

**Severity:** Low
**Status:** REPRODUCED (source-only confirmation — driver/HW-gated, not runtime-triggered on QEMU guest)
**Impact:** dos
**Confidence:** certain

## Verdict
REPRODUCED. The cited bug is confirmed real in the audited source at `sys/dev/drm/ttm/ttm_bo_vm.c:800-807`.

## Mechanism
ttm_bo_mmap_single calls ttm_bo_get_unless_zero (increments kref) but success path never calls ttm_bo_put; N mmaps of same BO leak N-1 krefs, pinning backing pages forever.

## Fix
Add ttm_bo_put(bo) on the mmap_single success path.

The full git-apply-able diff is in `fix.diff`.

## Build validation
fix.diff applies cleanly and compiles with `-Werror` as part of the batch module build
(all 51 fixes applied to /usr/src, kernel+modules built).

## Notes
Source-only confirmation: this finding is in a GPU/display code path that requires
specific hardware not present in the QEMU guest. The bug is confirmed by source tracing
(cited path:line verified against sys/), and the fix compiles clean. No runtime trigger
was attempted as the relevant device/module is HW-gated.