panic: Memory modified after free 0xfffff80012936600(256) val=0 @ 0xfffff80012936600

cpuid = 1
time = 1557873072
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe00212221c0
vpanic() at vpanic+0x1e0/frame 0xfffffe0021222220
panic() at panic+0x43/frame 0xfffffe0021222280
trash_ctor() at trash_ctor+0xaa/frame 0xfffffe00212222c0
mb_ctor_mbuf() at mb_ctor_mbuf+0x30/frame 0xfffffe0021222300
uma_zalloc_arg() at uma_zalloc_arg+0x1036/frame 0xfffffe00212223b0
tcp_m_copym() at tcp_m_copym+0x372/frame 0xfffffe0021222460
tcp_output() at tcp_output+0x1ef4/frame 0xfffffe0021222620
tcp_usr_send() at tcp_usr_send+0x71f/frame 0xfffffe00212226f0
sosend_generic() at sosend_generic+0x73d/frame 0xfffffe00212227c0
sosend() at sosend+0xc6/frame 0xfffffe0021222830
soo_write() at soo_write+0x61/frame 0xfffffe0021222870
dofilewrite() at dofilewrite+0xfd/frame 0xfffffe00212228d0
kern_writev() at kern_writev+0x66/frame 0xfffffe0021222910
sys_write() at sys_write+0xd2/frame 0xfffffe0021222980
amd64_syscall() at amd64_syscall+0x436/frame 0xfffffe0021222ab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe0021222ab0
--- syscall (4, FreeBSD ELF64, sys_write), rip = 0x80090d1ea, rsp = 0x7fffffffa528, rbp = 0x7fffffffa560 ---
KDB: enter: panic
[ thread pid 750 tid 100100 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why