------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28, CPU#0: syz.4.10358/31878
Modules linked in:
CPU: 0 UID: 0 PID: 31878 Comm: syz.4.10358 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28
Code: d4 8e 8f 0b 67 48 0f b9 3a eb 4a e8 68 ab f3 fc 48 8d 3d d1 8e 8f 0b 67 48 0f b9 3a eb 37 e8 55 ab f3 fc 48 8d 3d ce 8e 8f 0b <67> 48 0f b9 3a eb 24 e8 42 ab f3 fc 48 8d 3d cb 8e 8f 0b 67 48 0f
RSP: 0018:ffffc90000007c68 EFLAGS: 00010246
RAX: ffffffff84d3671b RBX: 0000000000000003 RCX: ffff888036660000
RDX: 0000000000000100 RSI: ffffffff8f365300 RDI: ffffffff9062f5f0
RBP: ffffc90000007d70 R08: ffff888036660000 R09: 0000000000000005
R10: 0000000000000004 R11: 0000000000000100 R12: 0000000000000000
R13: 00000001000145e0 R14: ffff8880539a7020 R15: ffff8880539a7258
FS:  00007f210adb46c0(0000) GS:ffff888124f4b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6e2cd5da08 CR3: 0000000025b32000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: fffffffffffffffc DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748
 expire_timers kernel/time/timer.c:1799 [inline]
 __run_timers kernel/time/timer.c:2374 [inline]
 __run_timer_base+0x652/0x8b0 kernel/time/timer.c:2386
 run_timer_base kernel/time/timer.c:2395 [inline]
 run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405
 handle_softirqs+0x225/0x840 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:188 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:206
Code: 90 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 aa 07 cf f5 48 89 df e8 02 7d cf f5 e8 bd 5d fb f5 fb bf 01 00 00 00 <e8> b2 90 c0 f5 65 8b 05 ab 60 99 07 85 c0 74 07 5b e9 11 48 00 00
RSP: 0018:ffffc90004a856f0 EFLAGS: 00000206
RAX: 000000000005cb39 RBX: ffff88801dadd318 RCX: 0000000080000001
RDX: 0000000000000006 RSI: ffffffff8e22f174 RDI: 0000000000000001
RBP: ffffc90004a85a50 R08: ffffffff90579d37 R09: 1ffffffff20af3a6
R10: dffffc0000000000 R11: fffffbfff20af3a7 R12: dffffc0000000000
R13: 0000000000000012 R14: 0000000000000000 R15: 0000000000000000
 spin_unlock_irq include/linux/spinlock.h:402 [inline]
 lruvec_unlock_irq include/linux/memcontrol.h:1529 [inline]
 evict_folios+0x3634/0x49e0 mm/vmscan.c:4829
 try_to_shrink_lruvec+0xb4f/0xed0 mm/vmscan.c:4983
 lru_gen_shrink_lruvec mm/vmscan.c:5128 [inline]
 shrink_lruvec+0x554/0x2a60 mm/vmscan.c:5888
 shrink_node_memcgs mm/vmscan.c:6127 [inline]
 shrink_node+0xa9b/0x3b60 mm/vmscan.c:6171
 shrink_zones mm/vmscan.c:6410 [inline]
 do_try_to_free_pages+0x6a3/0x1990 mm/vmscan.c:6472
 try_to_free_mem_cgroup_pages+0x30d/0x830 mm/vmscan.c:6794
 try_charge_memcg+0x86a/0x1590 mm/memcontrol.c:2655
 charge_memcg+0x19c/0x2b0 mm/memcontrol.c:5126
 __mem_cgroup_charge+0x25/0x80 mm/memcontrol.c:5143
 mem_cgroup_charge include/linux/memcontrol.h:657 [inline]
 shmem_alloc_and_add_folio+0x7bb/0xf60 mm/shmem.c:1969
 shmem_get_folio_gfp+0x5da/0x16d0 mm/shmem.c:2512
 shmem_get_folio mm/shmem.c:2618 [inline]
 shmem_write_begin+0x16c/0x330 mm/shmem.c:3249
 generic_perform_write+0x2d5/0x8f0 mm/filemap.c:4358
 shmem_file_write_iter+0xf8/0x120 mm/shmem.c:3424
 __kernel_write_iter+0x44a/0x8f0 fs/read_write.c:621
 dump_emit_page fs/coredump.c:1298 [inline]
 dump_user_range+0xc19/0x12c0 fs/coredump.c:1372
 elf_core_dump+0x3485/0x3a90 fs/binfmt_elf.c:2109
 coredump_write+0x1290/0x1960 fs/coredump.c:1052
 do_coredump fs/coredump.c:1131 [inline]
 vfs_coredump+0x36ff/0x44b0 fs/coredump.c:1200
 get_signal+0x1094/0x12c0 kernel/signal.c:3031
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:101 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
 irqentry_exit+0x2ba/0x8f0 kernel/entry/common.c:165
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0033:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 002b:0000200000000188 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007f210a225fa0 RCX: 00007f2109f9e019
RDX: 0000000000000000 RSI: 0000200000000180 RDI: 0000000000000200
RBP: 00007f210a03500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f210a226038 R14: 00007f210a225fa0 R15: 00007f210a34fa48
 </TASK>
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	8e 8f 0b 67 48 0f    	mov    0xf48670b(%rdi),%cs
   6:	b9 3a eb 4a e8       	mov    $0xe84aeb3a,%ecx
   b:	68 ab f3 fc 48       	push   $0x48fcf3ab
  10:	8d 3d d1 8e 8f 0b    	lea    0xb8f8ed1(%rip),%edi        # 0xb8f8ee7
  16:	67 48 0f b9 3a       	ud1    (%edx),%rdi
  1b:	eb 37                	jmp    0x54
  1d:	e8 55 ab f3 fc       	call   0xfcf3ab77
  22:	48 8d 3d ce 8e 8f 0b 	lea    0xb8f8ece(%rip),%rdi        # 0xb8f8ef7
* 29:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2e:	eb 24                	jmp    0x54
  30:	e8 42 ab f3 fc       	call   0xfcf3ab77
  35:	48 8d 3d cb 8e 8f 0b 	lea    0xb8f8ecb(%rip),%rdi        # 0xb8f8f07
  3c:	67                   	addr32
  3d:	48                   	rex.W
  3e:	0f                   	.byte 0xf