DF-3406 fix validation -- patched kernel #1 (Sat Sep 12 06:59:23 UTC 2026,
fix.diff = m_freem(m) on tapwrite's error path; combined with DF-3405 fix)

$ netstat -m | head -2
7/146632 mbufs in use (current/max):

$ /root/tapleak5 100000     (identical storm, unit tap5)
(the run takes several CPU-minutes: each iteration now also *frees*
 the spare mbuf, and every iteration still takes a VM protection fault)

$ netstat -m | head -3
7/146632 mbufs in use (current/max):
256/33552 mbuf clusters in use (current/max)

=> ZERO growth: 7 -> 7 after 100,000 EFAULT writes.
(baseline: 7 -> 100,007)