Kernel bug: WARNING: refcount bug in __add_used_btf
Subsystem: bpf
Status: fixed

Crash report:
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25, CPU#0: syz.1.44/6186
Modules linked in:
CPU: 0 UID: 0 PID: 6186 Comm: syz.1.44 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25
Code: eb 66 85 db 74 3e 83 fb 01 75 4c e8 2b 5b 23 fd 48 8d 3d 04 7d 58 0b 67 48 0f b9 3a eb 4a e8 18 5b 23 fd 48 8d 3d 01 7d 58 0b <67> 48 0f b9 3a eb 37 e8 05 5b 23 fd 48 8d 3d fe 7c 58 0b 67 48 0f
RSP: 0018:ffffc90003337380 EFLAGS: 00010293
RAX: ffffffff84a11b58 RBX: 0000000000000002 RCX: ffff88802f648000
RDX: 0000000000000000 RSI: ffffffff8ece7f00 RDI: ffffffff8ff99860
RBP: 0000000000000000 R08: ffff88802f648000 R09: 0000000000000005
R10: 0000000000000004 R11: 0000000000000000 R12: ffff8880762d8854
R13: 1ffff9200078f60c R14: ffff888079bc6258 R15: ffff888079bc6200
FS:  00007fb9d62266c0(0000) GS:ffff8881256f8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb9d53e8600 CR3: 00000000329a6000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __add_used_btf+0x152/0x2e0 kernel/bpf/verifier.c:21107
 check_pseudo_btf_id+0x764/0xbb0 kernel/bpf/verifier.c:21238
 resolve_pseudo_ldimm64+0x3f4/0xc90 kernel/bpf/verifier.c:21489
 bpf_check+0x1d82/0x1ce00 kernel/bpf/verifier.c:25715
 bpf_prog_load+0x1484/0x1ae0 kernel/bpf/syscall.c:3081
 __sys_bpf+0x618/0x950 kernel/bpf/syscall.c:6218
 __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: 0033:0x7fb9d539aeb9
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:00007fb9d6226028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fb9d5615fa0 RCX: 00007fb9d539aeb9
RDX: 0000000000000094 RSI: 0000200000000180 RDI: 0000000000000005
RBP: 00007fb9d5408c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb9d5616038 R14: 00007fb9d5615fa0 R15: 00007ffda6487988
 </TASK>
----------------
Code disassembly (best guess):
   0:	eb 66                	jmp    0x68
   2:	85 db                	test   %ebx,%ebx
   4:	74 3e                	je     0x44
   6:	83 fb 01             	cmp    $0x1,%ebx
   9:	75 4c                	jne    0x57
   b:	e8 2b 5b 23 fd       	call   0xfd235b3b
  10:	48 8d 3d 04 7d 58 0b 	lea    0xb587d04(%rip),%rdi        # 0xb587d1b
  17:	67 48 0f b9 3a       	ud1    (%edx),%rdi
  1c:	eb 4a                	jmp    0x68
  1e:	e8 18 5b 23 fd       	call   0xfd235b3b
  23:	48 8d 3d 01 7d 58 0b 	lea    0xb587d01(%rip),%rdi        # 0xb587d2b
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	eb 37                	jmp    0x68
  31:	e8 05 5b 23 fd       	call   0xfd235b3b
  36:	48 8d 3d fe 7c 58 0b 	lea    0xb587cfe(%rip),%rdi        # 0xb587d3b
  3d:	67                   	addr32
  3e:	48                   	rex.W
  3f:	0f                   	.byte 0xf