panic: mtx_lock() of spin mutex (null) @ /syzkaller/managers/main/kernel/sys/netinet/sctputil.c:4531
cpuid = 0
time = 1553233440
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe00212c2570
vpanic() at vpanic+0x1e0/frame 0xfffffe00212c25d0
panic() at panic+0x43/frame 0xfffffe00212c2630
__mtx_lock_flags() at __mtx_lock_flags+0x1fd/frame 0xfffffe00212c2690
sctp_add_to_readq() at sctp_add_to_readq+0x620/frame 0xfffffe00212c2710
sctp_ulp_notify() at sctp_ulp_notify+0xe75/frame 0xfffffe00212c2780
sctp_setopt() at sctp_setopt+0x99d0/frame 0xfffffe00212c2810
sctp_ctloutput() at sctp_ctloutput+0x214/frame 0xfffffe00212c2850
sosetopt() at sosetopt+0x101/frame 0xfffffe00212c28d0
kern_setsockopt() at kern_setsockopt+0x158/frame 0xfffffe00212c2950
sys_setsockopt() at sys_setsockopt+0x33/frame 0xfffffe00212c2980
amd64_syscall() at amd64_syscall+0x436/frame 0xfffffe00212c2ab0
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe00212c2ab0
--- syscall (198, FreeBSD ELF64, nosys), rip = 0x412e7a, rsp = 0x7fffdffbbf38, rbp = 0x5 ---
KDB: enter: panic
[ thread pid 873 tid 100240 ]
Stopped at      kdb_enter+0x6a: movq    $0,kdb_why
db>