kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
CPU: 0 PID: 15727 Comm: syz-executor948 Not tainted 4.18.0-rc3+ #47
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:free_start_sg kernel/bpf/sockmap.c:586 [inline]
RIP: 0010:bpf_tcp_close+0x2bf/0x1050 kernel/bpf/sockmap.c:330
Code: 
------------[ cut here ]------------
Bad or missing usercopy whitelist? Kernel memory overwrite attempt detected to SLAB object 'TCPv6' (offset 1392, size 64)!
WARNING: CPU: 0 PID: 15727 at mm/usercopy.c:81 usercopy_warn+0xf5/0x120 mm/usercopy.c:76
Kernel panic - not syncing: panic_on_warn set ...

Shutting down cpus with NMI
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..