panic: sx_xlock() of destroyed sx @ /syzkaller/managers/main/kernel/sys/kern/uipc_sockbuf.c:285
cpuid = 1
time = 1559825715
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe001f6ea5c0
vpanic() at vpanic+0x1e0/frame 0xfffffe001f6ea620
panic() at panic+0x43/frame 0xfffffe001f6ea680
_sx_xlock() at _sx_xlock+0x1c9/frame 0xfffffe001f6ea6d0
sosend_generic() at sosend_generic+0x1a0/frame 0xfffffe001f6ea7a0
sosend() at sosend+0xc6/frame 0xfffffe001f6ea810
kern_sendit() at kern_sendit+0x35e/frame 0xfffffe001f6ea8c0
sendit() at sendit+0x225/frame 0xfffffe001f6ea920
sys_sendto() at sys_sendto+0x5c/frame 0xfffffe001f6ea980
amd64_syscall() at amd64_syscall+0x436/frame 0xfffffe001f6eaab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe001f6eaab0
--- syscall (198, FreeBSD ELF64, nosys), rip = 0x4131ba, rsp = 0x7fffdfffdf38, rbp = 0x6 ---
KDB: enter: panic
[ thread pid 862 tid 100152 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why