------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 2271 at lib/refcount.c:187 refcount_sub_and_test+0x2d3/0x330 lib/refcount.c:187
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 2271 Comm: syz-executor7 Not tainted 4.17.0+ #39
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
 panic+0x22f/0x4de kernel/panic.c:184
 __warn.cold.8+0x163/0x1b3 kernel/panic.c:536
 report_bug+0x252/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:refcount_sub_and_test+0x2d3/0x330 lib/refcount.c:187
Code: 89 de e8 40 7e 21 fe 84 db 74 07 31 db e9 52 ff ff ff e8 60 7d 21 fe 48 c7 c7 20 4b 1a 88 c6 05 78 64 40 06 01 e8 8d 97 ed fd <0f> 0b 31 db e9 31 ff ff ff 48 8b bd 28 ff ff ff 89 85 34 ff ff ff 
RSP: 0018:ffff8801986ff800 EFLAGS: 00010282
RAX: 0000000000000026 RBX: 0000000000000000 RCX: ffffc90002427000
RDX: 0000000000003cd9 RSI: ffffffff8161f371 RDI: ffff8801986ff4d8
RBP: ffff8801986ff8e8 R08: ffff8801b0f30400 R09: 0000000000000006
R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
R13: ffff8801986ff8c0 R14: 0000000000000001 R15: ffff8801ca23df80
 refcount_dec_and_test+0x1a/0x20 lib/refcount.c:212
 smap_release_sock+0x6e/0x2f0 kernel/bpf/sockmap.c:1358
 sock_hash_ctx_update_elem.isra.24+0x896/0x1560 kernel/bpf/sockmap.c:2281
 sock_hash_update_elem+0x14f/0x2d0 kernel/bpf/sockmap.c:2303
 map_update_elem+0x5c4/0xc90 kernel/bpf/syscall.c:765
 __do_sys_bpf kernel/bpf/syscall.c:2357 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:2328 [inline]
 __x64_sys_bpf+0x32d/0x510 kernel/bpf/syscall.c:2328
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455a99
Code: 1d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007f5855c31c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f5855c326d4 RCX: 0000000000455a99
RDX: 0000000000000020 RSI: 0000000020000180 RDI: 0000000000000002
RBP: 000000000072bf48 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004bb77f R14: 00000000004c8490 R15: 0000000000000001
Dumping ftrace buffer:
---------------------------------
syz-exec-7192    1...2 57169162us : 0: }D
syz-exec-7192    1...2 57169167us : 0: }D
syz-exec-7192    1...2 57169171us : 0: }D
---------------------------------
Kernel Offset: disabled
Rebooting in 86400 seconds..