==================================================================
BUG: KASAN: use-after-free in atomic_fetch_add include/asm-generic/atomic-instrumented.h:111 [inline]
BUG: KASAN: use-after-free in refcount_add include/linux/refcount.h:188 [inline]
BUG: KASAN: use-after-free in refcount_inc include/linux/refcount.h:228 [inline]
BUG: KASAN: use-after-free in get_task_struct include/linux/sched/task.h:112 [inline]
BUG: KASAN: use-after-free in kthread_stop+0x37/0x4a0 kernel/kthread.c:612
Write of size 4 at addr ffff8881ec013f20 by task syz-executor.4/368

CPU: 0 PID: 368 Comm: syz-executor.4 Not tainted 5.4.268-syzkaller-00003-g2d5d8240a7cb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1d8/0x241 lib/dump_stack.c:118
 print_address_description+0x8c/0x600 mm/kasan/report.c:384
 __kasan_report+0xf3/0x120 mm/kasan/report.c:516
 kasan_report+0x30/0x60 mm/kasan/common.c:653
 check_memory_region_inline mm/kasan/generic.c:141 [inline]
 check_memory_region+0x272/0x280 mm/kasan/generic.c:191
 atomic_fetch_add include/asm-generic/atomic-instrumented.h:111 [inline]
 refcount_add include/linux/refcount.h:188 [inline]
 refcount_inc include/linux/refcount.h:228 [inline]
 get_task_struct include/linux/sched/task.h:112 [inline]
 kthread_stop+0x37/0x4a0 kernel/kthread.c:612
 ext4_put_super+0x790/0xbb0 fs/ext4/super.c:1055
 generic_shutdown_super+0x120/0x2a0 fs/super.c:464
 kill_block_super+0x7a/0xe0 fs/super.c:1453
 deactivate_locked_super+0xa8/0x110 fs/super.c:335
 deactivate_super+0x1e2/0x2a0 fs/super.c:366
 cleanup_mnt+0x44e/0x500 fs/namespace.c:1102
 task_work_run+0x140/0x170 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x190/0x1a0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode+0x199/0x200 arch/x86/entry/common.c:194
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1

Allocated by task 2:
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 __kasan_kmalloc+0x171/0x210 mm/kasan/common.c:529
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc_node mm/slub.c:2829 [inline]
 slab_alloc mm/slub.c:2837 [inline]
 kmem_cache_alloc+0xd9/0x250 mm/slub.c:2842
 kmem_cache_alloc_node include/linux/slab.h:427 [inline]
 alloc_task_struct_node kernel/fork.c:171 [inline]
 dup_task_struct+0x4f/0x600 kernel/fork.c:882
 copy_process+0x56d/0x3230 kernel/fork.c:1889
 _do_fork+0x197/0x900 kernel/fork.c:2399
 kernel_thread+0x16a/0x1d0 kernel/fork.c:2489
 create_kthread kernel/kthread.c:311 [inline]
 kthreadd+0x3b1/0x4f0 kernel/kthread.c:654
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:354

Freed by task 0:
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 kasan_set_free_info mm/kasan/common.c:345 [inline]
 __kasan_slab_free+0x1b5/0x270 mm/kasan/common.c:487
 slab_free_hook mm/slub.c:1455 [inline]
 slab_free_freelist_hook mm/slub.c:1494 [inline]
 slab_free mm/slub.c:3080 [inline]
 kmem_cache_free+0x10b/0x2c0 mm/slub.c:3096
 __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
 rcu_do_batch+0x492/0xa00 kernel/rcu/tree.c:2167
 rcu_core+0x4c8/0xcb0 kernel/rcu/tree.c:2387
 __do_softirq+0x23b/0x6b7 kernel/softirq.c:292

The buggy address belongs to the object at ffff8881ec013f00
 which belongs to the cache task_struct of size 3904
The buggy address is located 32 bytes inside of
 3904-byte region [ffff8881ec013f00, ffff8881ec014e40)
The buggy address belongs to the page:
page:ffffea0007b00400 refcount:1 mapcount:0 mapping:ffff8881f5cf8c80 index:0x0 compound_mapcount: 0
flags: 0x8000000000010200(slab|head)
raw: 8000000000010200 dead000000000100 dead000000000122 ffff8881f5cf8c80
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL)
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook mm/page_alloc.c:2165 [inline]
 prep_new_page+0x18f/0x370 mm/page_alloc.c:2171
 get_page_from_freelist+0x2d13/0x2d90 mm/page_alloc.c:3794
 __alloc_pages_nodemask+0x393/0x840 mm/page_alloc.c:4891
 alloc_slab_page+0x39/0x3c0 mm/slub.c:343
 allocate_slab mm/slub.c:1683 [inline]
 new_slab+0x97/0x440 mm/slub.c:1749
 new_slab_objects mm/slub.c:2505 [inline]
 ___slab_alloc+0x2fe/0x490 mm/slub.c:2667
 __slab_alloc+0x62/0xa0 mm/slub.c:2707
 slab_alloc_node mm/slub.c:2792 [inline]
 slab_alloc mm/slub.c:2837 [inline]
 kmem_cache_alloc+0x109/0x250 mm/slub.c:2842
 kmem_cache_alloc_node include/linux/slab.h:427 [inline]
 alloc_task_struct_node kernel/fork.c:171 [inline]
 dup_task_struct+0x4f/0x600 kernel/fork.c:882
 copy_process+0x56d/0x3230 kernel/fork.c:1889
 _do_fork+0x197/0x900 kernel/fork.c:2399
 kernel_thread+0x16a/0x1d0 kernel/fork.c:2489
 create_kthread kernel/kthread.c:311 [inline]
 kthreadd+0x3b1/0x4f0 kernel/kthread.c:654
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:354
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1176 [inline]
 __free_pages_ok+0x847/0x950 mm/page_alloc.c:1438
 free_the_page mm/page_alloc.c:4953 [inline]
 __free_pages+0x91/0x140 mm/page_alloc.c:4959
 free_thread_stack kernel/fork.c:299 [inline]
 release_task_stack kernel/fork.c:439 [inline]
 put_task_stack+0x212/0x260 kernel/fork.c:450
 finish_task_switch+0x24a/0x590 kernel/sched/core.c:3479
 context_switch kernel/sched/core.c:3611 [inline]
 __schedule+0xb0d/0x1320 kernel/sched/core.c:4307
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:4456
 preempt_schedule+0xd9/0xe0 kernel/sched/core.c:4481
 ___preempt_schedule+0x16/0x20 arch/x86/entry/thunk_64.S:50
 unwind_next_frame+0x19c2/0x1ea0 arch/x86/kernel/unwind_orc.c:603
 arch_stack_walk+0x111/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x118/0x1c0 kernel/stacktrace.c:123
 save_stack mm/kasan/common.c:70 [inline]
 set_track mm/kasan/common.c:78 [inline]
 __kasan_kmalloc+0x171/0x210 mm/kasan/common.c:529
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc_node mm/slub.c:2829 [inline]
 slab_alloc mm/slub.c:2837 [inline]
 kmem_cache_alloc_trace+0xdc/0x260 mm/slub.c:2854
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:690 [inline]
 kernfs_fop_open+0x31c/0xac0 fs/kernfs/file.c:647
 do_dentry_open+0x964/0x1130 fs/open.c:796
 do_last fs/namei.c:3515 [inline]
 path_openat+0x2992/0x3480 fs/namei.c:3634

Memory state around the buggy address:
 ffff8881ec013e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881ec013e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881ec013f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8881ec013f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881ec014000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 368 at lib/refcount.c:25 refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25
Modules linked in:
CPU: 0 PID: 368 Comm: syz-executor.4 Tainted: G    B             5.4.268-syzkaller-00003-g2d5d8240a7cb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:refcount_warn_saturate+0x132/0x1a0 lib/refcount.c:25
Code: 04 01 48 c7 c7 a0 02 fa 84 e8 aa 16 0e ff 0f 0b eb a9 e8 91 5f 37 ff c6 05 24 aa 1c 04 01 48 c7 c7 20 03 fa 84 e8 8e 16 0e ff <0f> 0b eb 8d e8 75 5f 37 ff c6 05 09 aa 1c 04 01 48 c7 c7 80 03 fa
RSP: 0018:ffff8881d5e2fc30 EFLAGS: 00010246
RAX: 9a0ea50002b96600 RBX: 0000000000000002 RCX: ffff8881d5e21f80
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000002 R08: ffffffff814d6872 R09: ffffed103edca9b8
R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000
R13: ffff8881ec013f00 R14: dffffc0000000000 R15: ffff8881ec013f20
FS:  0000555556d31480(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c002a70000 CR3: 00000001d5d88000 CR4: 00000000003406b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 refcount_add include/linux/refcount.h:192 [inline]
 refcount_inc include/linux/refcount.h:228 [inline]
 get_task_struct include/linux/sched/task.h:112 [inline]
 kthread_stop+0x1a5/0x4a0 kernel/kthread.c:612
 ext4_put_super+0x790/0xbb0 fs/ext4/super.c:1055
 generic_shutdown_super+0x120/0x2a0 fs/super.c:464
 kill_block_super+0x7a/0xe0 fs/super.c:1453
 deactivate_locked_super+0xa8/0x110 fs/super.c:335
 deactivate_super+0x1e2/0x2a0 fs/super.c:366
 cleanup_mnt+0x44e/0x500 fs/namespace.c:1102
 task_work_run+0x140/0x170 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x190/0x1a0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode+0x199/0x200 arch/x86/entry/common.c:194
 entry_SYSCALL_64_after_hwframe+0x5c/0xc1
---[ end trace be3f6db1e0f68687 ]---