------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 8416 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Modules linked in:

CPU: 1 PID: 8416 Comm: systemd-sysctl Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Code: e9 db fe ff ff 48 89 df e8 3c de ee fd e9 8a fe ff ff e8 a2 be aa fd 48 c7 c7 40 eb c1 89 c6 05 3c a2 e8 09 01 e8 b8 40 ff 04 <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55
RSP: 0018:ffffc90000dc0e10 EFLAGS: 00010286

RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888020df54c0 RSI: ffffffff815c5205 RDI: fffff520001b81b4
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815bdf9e R11: 0000000000000000 R12: ffff888019930000
R13: ffff8880159c25b0 R14: ffff888021e114a0 R15: 0000000000000000
FS:  00007fb2f18558c0(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055632c2db268 CR3: 0000000026431000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 put_signal_struct kernel/fork.c:724 [inline]
 __put_task_struct+0x34f/0x400 kernel/fork.c:741
 put_task_struct include/linux/sched/task.h:113 [inline]
 delayed_put_task_struct+0x1f6/0x340 kernel/exit.c:173
 rcu_do_batch kernel/rcu/tree.c:2559 [inline]
 rcu_core+0x74a/0x12f0 kernel/rcu/tree.c:2794
 __do_softirq+0x29b/0x9f6 kernel/softirq.c:345
 invoke_softirq kernel/softirq.c:221 [inline]
 __irq_exit_rcu kernel/softirq.c:422 [inline]
 irq_exit_rcu+0x134/0x200 kernel/softirq.c:434
 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1100
 </IRQ>
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x38/0x70 kernel/locking/spinlock.c:191
Code: 74 24 10 e8 ca cd 4d f8 48 89 ef e8 02 84 4e f8 81 e3 00 02 00 00 75 25 9c 58 f6 c4 02 75 2d 48 85 db 74 01 fb bf 01 00 00 00 <e8> e3 51 42 f8 65 8b 05 ac 17 f6 76 85 c0 74 0a 5b 5d c3 e8 50 0d
RSP: 0018:ffffc900016afa08 EFLAGS: 00000206

RAX: 0000000000000006 RBX: 0000000000000200 RCX: 1ffffffff1b8bba1
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffffffff900ade58 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff8179e5a8 R11: 000000000000003f R12: 1ffffffff2015bca
R13: 0000000000000000 R14: dead000000000100 R15: dffffc0000000000
 __debug_check_no_obj_freed lib/debugobjects.c:997 [inline]
 debug_check_no_obj_freed+0x20c/0x420 lib/debugobjects.c:1018
 slab_free_hook mm/slub.c:1554 [inline]
 slab_free_freelist_hook+0x147/0x210 mm/slub.c:1600
 slab_free mm/slub.c:3161 [inline]
 kmem_cache_free+0x8a/0x740 mm/slub.c:3177
 putname+0xe1/0x120 fs/namei.c:259
 filename_lookup+0x3c3/0x570 fs/namei.c:2465
 user_path_at include/linux/namei.h:60 [inline]
 vfs_statx+0x142/0x390 fs/stat.c:195
 vfs_fstatat fs/stat.c:217 [inline]
 vfs_lstat include/linux/fs.h:3240 [inline]
 __do_sys_newlstat+0x91/0x110 fs/stat.c:372
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7fb2f0f40335
Code: 69 db 2b 00 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 83 ff 01 48 89 f0 77 30 48 89 c7 48 89 d6 b8 06 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 03 f3 c3 90 48 8b 15 31 db 2b 00 f7 d8 64 89
RSP: 002b:00007ffefdd21178 EFLAGS: 00000246
 ORIG_RAX: 0000000000000006
RAX: ffffffffffffffda RBX: 000055632c2db260 RCX: 00007fb2f0f40335
RDX: 00007ffefdd211b0 RSI: 00007ffefdd211b0 RDI: 000055632c2da260
RBP: 00007ffefdd21270 R08: 0000000000000003 R09: 0000000000001010
R10: 0000000000000030 R11: 0000000000000246 R12: 000055632c2da260
R13: 000055632c2da264 R14: 000055632c2d9161 R15: 000055632c2d9164
irq event stamp: 12260
hardirqs last  enabled at (12260): [<ffffffff815c34cb>] console_trylock_spinning kernel/printk/printk.c:1811 [inline]
hardirqs last  enabled at (12260): [<ffffffff815c34cb>] vprintk_emit+0x53b/0x560 kernel/printk/printk.c:2097
hardirqs last disabled at (12259): [<ffffffff815c341e>] console_trylock_spinning kernel/printk/printk.c:1779 [inline]
hardirqs last disabled at (12259): [<ffffffff815c341e>] vprintk_emit+0x48e/0x560 kernel/printk/printk.c:2097
softirqs last  enabled at (11402): [<ffffffff86f8b8fe>] sock_setsockopt+0x20e/0x2810 net/core/sock.c:1269