------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 0 PID: 17747 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25 Modules linked in: CPU: 0 UID: 0 PID: 17747 Comm: syz.0.4858 Not tainted 6.16.0-rc4-syzkaller-g6b9fd8857b9f #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 RIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25 Code: 00 00 e8 39 93 fe fc 5b 41 5e e9 d1 65 b1 06 cc e8 2b 93 fe fc c6 05 7b 2d ca 0a 01 90 48 c7 c7 00 45 e2 8b e8 47 3a c2 fc 90 <0f> 0b 90 90 eb d7 e8 0b 93 fe fc c6 05 5c 2d ca 0a 01 90 48 c7 c7 RSP: 0018:ffffc90004f17c88 EFLAGS: 00010246 RAX: fdff50f1fa4c5600 RBX: 0000000000000002 RCX: ffff888026115a00 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002 RBP: ffffc90004f17d90 R08: 0000000000000003 R09: 0000000000000004 R10: dffffc0000000000 R11: fffffbfff1bfa9fc R12: 1ffff110048a4605 R13: 1ffff920009e2f9c R14: ffff888034c7b4c8 R15: dffffc0000000000 FS: 00007f1bffbf46c0(0000) GS:ffff888125c16000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1bffbd3d58 CR3: 000000005e9f8000 CR4: 00000000003526f0 Call Trace: ax25_setsockopt+0xabb/0xc20 net/ax25/af_ax25.c:705 do_sock_setsockopt+0x257/0x3e0 net/socket.c:2344 __sys_setsockopt net/socket.c:2369 [inline] __do_sys_setsockopt net/socket.c:2375 [inline] __se_sys_setsockopt net/socket.c:2372 [inline] __x64_sys_setsockopt+0x18b/0x220 net/socket.c:2372 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f1bfed8d169 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f1bffbf4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 00007f1bfefa5fa0 RCX: 00007f1bfed8d169 RDX: 0000000000000019 RSI: 0000000000000101 RDI: 0000000000000004 RBP: 00007f1bfee0e990 R08: 0000000000000010 R09: 0000000000000000 R10: 0000200000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f1bfefa5fa0 R15: 00007ffe6fa91688