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BUG: KASAN: slab-use-after-free in __ref_is_percpu include/linux/percpu-refcount.h:174 [inline]
BUG: KASAN: slab-use-after-free in percpu_ref_put_many include/linux/percpu-refcount.h:332 [inline]
BUG: KASAN: slab-use-after-free in percpu_ref_put+0xda/0x250 include/linux/percpu-refcount.h:351
Read of size 8 at addr ffff8880002fa0b0 by task kworker/u4:3/46

CPU: 0 UID: 0 PID: 46 Comm: kworker/u4:3 Not tainted 6.12.0-syzkaller-00971-g158f238aa69d #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: loop0 loop_rootcg_workfn
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 __ref_is_percpu include/linux/percpu-refcount.h:174 [inline]
 percpu_ref_put_many include/linux/percpu-refcount.h:332 [inline]
 percpu_ref_put+0xda/0x250 include/linux/percpu-refcount.h:351
 blk_update_request+0x5e5/0x1160 block/blk-mq.c:981
 blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1143
 loop_handle_cmd drivers/block/loop.c:1926 [inline]
 loop_process_work+0x1bc8/0x21c0 drivers/block/loop.c:1944
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
 worker_thread+0x870/0xd30 kernel/workqueue.c:3391
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Allocated by task 5327:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:257 [inline]
 __kmalloc_cache_noprof+0x19c/0x2c0 mm/slub.c:4295
 kmalloc_noprof include/linux/slab.h:878 [inline]
 kzalloc_noprof include/linux/slab.h:1014 [inline]
 __bch2_dev_alloc+0x57/0xa60 fs/bcachefs/super.c:1304
 bch2_dev_alloc+0xd4/0x170 fs/bcachefs/super.c:1374
 bch2_fs_alloc fs/bcachefs/super.c:939 [inline]
 bch2_fs_open+0x2e3f/0x2f80 fs/bcachefs/super.c:2065
 bch2_fs_get_tree+0x738/0x1710 fs/bcachefs/fs.c:2157
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5327:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
 poison_slab_object mm/kasan/common.c:247 [inline]
 __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264
 kasan_slab_free include/linux/kasan.h:230 [inline]
 slab_free_hook mm/slub.c:2342 [inline]
 slab_free mm/slub.c:4579 [inline]
 kfree+0x1a0/0x440 mm/slub.c:4727
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x22f/0x480 lib/kobject.c:737
 bch2_fs_free+0x27b/0x3c0 fs/bcachefs/super.c:667
 bch2_fs_get_tree+0xd9f/0x1710 fs/bcachefs/fs.c:2265
 vfs_get_tree+0x90/0x2b0 fs/super.c:1814
 do_new_mount+0x2be/0xb40 fs/namespace.c:3507
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4034
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880002fa000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 176 bytes inside of
 freed 4096-byte region [ffff8880002fa000, ffff8880002fb000)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2f8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x7ff00000000040(head|node=0|zone=0|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 007ff00000000040 ffff88801ac42140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000040004 00000001f5000000 0000000000000000
head: 007ff00000000040 ffff88801ac42140 dead000000000100 dead000000000122
head: 0000000000000000 0000000000040004 00000001f5000000 0000000000000000
head: 007ff00000000003 ffffea000000be01 ffffffffffffffff 0000000000000000
head: 0000000000000008 0000000000000000 00000000ffffffff 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 7920887722, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0x3649/0x3790 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 alloc_slab_page+0x6a/0x140 mm/slub.c:2412
 allocate_slab+0x5a/0x2f0 mm/slub.c:2578
 new_slab mm/slub.c:2631 [inline]
 ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3818
 __slab_alloc+0x58/0xa0 mm/slub.c:3908
 __slab_alloc_node mm/slub.c:3961 [inline]
 slab_alloc_node mm/slub.c:4122 [inline]
 __kmalloc_cache_noprof+0x1d5/0x2c0 mm/slub.c:4290
 kmalloc_noprof include/linux/slab.h:878 [inline]
 kzalloc_noprof include/linux/slab.h:1014 [inline]
 kobject_uevent_env+0x28b/0x8e0 lib/kobject_uevent.c:540
 tty_register_device_attr+0x583/0x960 drivers/tty/tty_io.c:3296
 tty_register_device drivers/tty/tty_io.c:3210 [inline]
 tty_register_driver+0x5f6/0xc30 drivers/tty/tty_io.c:3473
 legacy_pty_init+0x3c7/0x610 drivers/tty/pty.c:581
 pty_init+0xe/0x20 drivers/tty/pty.c:943
 do_one_initcall+0x248/0x880 init/main.c:1269
 do_initcall_level+0x157/0x210 init/main.c:1331
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880002f9f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880002fa000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880002fa080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff8880002fa100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880002fa180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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