------------[ cut here ]------------
(skb->_skb_refdst & ~(1UL)) && !(skb->_skb_refdst & 1UL)
WARNING: ./include/linux/skbuff.h:1171 at skb_dst_check_unset include/linux/skbuff.h:1170 [inline], CPU#1: syz.0.17/5978
WARNING: ./include/linux/skbuff.h:1171 at skb_dst_set+0xfd/0x140 include/linux/skbuff.h:1217, CPU#1: syz.0.17/5978
Modules linked in:
CPU: 1 UID: 0 PID: 5978 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:skb_dst_check_unset include/linux/skbuff.h:1170 [inline]
RIP: 0010:skb_dst_set+0xfd/0x140 include/linux/skbuff.h:1217
Code: 2d 00 00 74 08 4c 89 f7 e8 80 13 98 f8 49 89 1e 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 64 5c 30 f8 90 <0f> 0b 90 e9 6d ff ff ff 44 89 e1 80 e1 07 38 c1 7c 8f be 04 00 00
RSP: 0018:ffffc90005367b58 EFLAGS: 00010293
RAX: ffffffff89923bbc RBX: dffffc0000000001 RCX: ffff8881037d8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 1ffff1102edaad5b R08: ffffffff8fced777 R09: 1ffffffff1f9daee
R10: dffffc0000000000 R11: ffffffff817422b0 R12: 0000000000000000
R13: ffff888176d56b01 R14: ffff888176d56ad8 R15: ffff888176d56a80
FS:  0000555564e8a500(0000) GS:ffff8882a9928000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fe63fff CR3: 000000016852c000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 bpf_prog_test_run_skb+0xe46/0x1ea0 net/bpf/test_run.c:1166
 bpf_prog_test_run+0x2c7/0x340 kernel/bpf/syscall.c:4714
 __sys_bpf+0x643/0x950 kernel/bpf/syscall.c:6236
 __do_sys_bpf kernel/bpf/syscall.c:6331 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6329 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6329
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f51a119acb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff3a40e428 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f51a1415fa0 RCX: 00007f51a119acb9
RDX: 0000000000000050 RSI: 00002000000003c0 RDI: 000000000000000a
RBP: 00007f51a1208bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f51a1415fac R14: 00007f51a1415fa0 R15: 00007f51a1415fa0
 </TASK>