syzbot

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refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 6618 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25
Modules linked in:
CPU: 1 UID: 0 PID: 6618 Comm: syz.1.492 Not tainted 6.16.0-rc7-syzkaller-00100-gafd8c2c9e2e2 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25
Code: 00 00 e8 e9 c2 ff fc 5b 41 5e c3 cc cc cc cc cc e8 db c2 ff fc c6 05 2d 6a cb 0a 01 90 48 c7 c7 c0 42 e2 8b e8 37 b2 c3 fc 90 <0f> 0b 90 90 eb d7 e8 bb c2 ff fc c6 05 0e 6a cb 0a 01 90 48 c7 c7
RSP: 0018:ffffc9000d097d48 EFLAGS: 00010246
RAX: a70fbede0ffcdb00 RBX: 0000000000000002 RCX: ffff88801eb1da00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc9000d097e48 R08: ffff8880b8724293 R09: 1ffff110170e4852
R10: dffffc0000000000 R11: ffffed10170e4853 R12: 1ffff11006b15f05
R13: 1ffff92001a12fb4 R14: ffff8880355296c8 R15: dffffc0000000000
FS:  00005555931e2500(0000) GS:ffff888125d23000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa4413802d8 CR3: 0000000075992000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ax25_setsockopt+0xabb/0xc20 net/ax25/af_ax25.c:705
 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2296
 __sys_setsockopt net/socket.c:2321 [inline]
 __do_sys_setsockopt net/socket.c:2327 [inline]
 __se_sys_setsockopt net/socket.c:2324 [inline]
 __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2324
 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: 0033:0x7f321f98e9a9
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:00007ffe0aab2ec8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007f321fbb5fa0 RCX: 00007f321f98e9a9
RDX: 0000000000000019 RSI: 0000000000000101 RDI: 000000000000000c
RBP: 00007f321fa10d69 R08: 0000000000000010 R09: 0000000000000000
R10: 00002000000001c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f321fbb5fa0 R14: 00007f321fbb5fa0 R15: 0000000000000005
 </TASK>