==================================================================
BUG: KASAN: slab-use-after-free in sync_blockdev_nowait+0x40/0x64 block/bdev.c:248
Read of size 8 at addr ffff0000c154b9b8 by task syz-executor/6555

CPU: 0 UID: 0 PID: 6555 Comm: syz-executor Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xa8/0x238 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:482
 kasan_report+0xb0/0x110 mm/kasan/report.c:595
 __asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
 sync_blockdev_nowait+0x40/0x64 block/bdev.c:248
 sync_filesystem+0x13c/0x218 fs/sync.c:60
 generic_shutdown_super+0x70/0x2b8 fs/super.c:622
 bch2_kill_sb+0x40/0x58 fs/bcachefs/fs.c:2618
 deactivate_locked_super+0xc4/0x12c fs/super.c:474
 deactivate_super+0xe0/0x100 fs/super.c:507
 cleanup_mnt+0x31c/0x3ac fs/namespace.c:1375
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1382
 task_work_run+0x1dc/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xfc/0x168 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 arm64_exit_to_user_mode arch/arm64/kernel/entry-common.c:103 [inline]
 el0_svc+0x170/0x254 arch/arm64/kernel/entry-common.c:745
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_alloc_info+0x44/0x54 mm/kasan/generic.c:562
 unpoison_slab_object mm/kasan/common.c:330 [inline]
 __kasan_slab_alloc+0x70/0x88 mm/kasan/common.c:356
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4191 [inline]
 slab_alloc_node mm/slub.c:4240 [inline]
 kmem_cache_alloc_lru_noprof+0x23c/0x3ec mm/slub.c:4259
 bdev_alloc_inode+0x30/0xa0 block/bdev.c:364
 alloc_inode+0x68/0x19c fs/inode.c:346
 new_inode+0x2c/0x130 fs/inode.c:1145
 bdev_alloc+0x34/0x338 block/bdev.c:461
 __alloc_disk_node+0x100/0x43c block/genhd.c:1465
 __blk_mq_alloc_disk+0x1bc/0x304 block/blk-mq.c:4451
 loop_add+0x324/0x880 drivers/block/loop.c:2043
 loop_init+0xe8/0x10c drivers/block/loop.c:2278
 do_one_initcall+0x250/0x990 init/main.c:1269
 do_initcall_level+0x128/0x1c4 init/main.c:1331
 do_initcalls+0x70/0xd0 init/main.c:1347
 do_basic_setup+0x78/0x8c init/main.c:1366
 kernel_init_freeable+0x268/0x39c init/main.c:1579
 kernel_init+0x24/0x1dc init/main.c:1469
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Freed by task 15:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x40/0x78 mm/kasan/common.c:68
 kasan_save_free_info+0x58/0x70 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x74/0x98 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2422 [inline]
 slab_free mm/slub.c:4695 [inline]
 kmem_cache_free+0x184/0x550 mm/slub.c:4797
 bdev_free_inode+0x178/0x1d8 block/bdev.c:394
 i_callback+0x50/0x78 fs/inode.c:325
 rcu_do_batch kernel/rcu/tree.c:2605 [inline]
 rcu_core+0x840/0x17d0 kernel/rcu/tree.c:2861
 rcu_core_si+0x10/0x1c kernel/rcu/tree.c:2878
 handle_softirqs+0x328/0xc88 kernel/softirq.c:579
 run_ksoftirqd+0x70/0xc0 kernel/softirq.c:968
 smpboot_thread_fn+0x4d8/0x9cc kernel/smpboot.c:160
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Last potentially related work creation:
 kasan_save_stack+0x40/0x6c mm/kasan/common.c:47
 kasan_record_aux_stack+0xb0/0xc8 mm/kasan/generic.c:548
 __call_rcu_common kernel/rcu/tree.c:3123 [inline]
 call_rcu+0x100/0x978 kernel/rcu/tree.c:3243
 destroy_inode fs/inode.c:401 [inline]
 evict+0x754/0x928 fs/inode.c:834
 iput_final fs/inode.c:1897 [inline]
 iput+0x6e4/0x83c fs/inode.c:1923
 bdev_drop+0x20/0x30 block/bdev.c:513
 disk_release+0x240/0x268 block/genhd.c:1313
 device_release+0x8c/0x1ac drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x2b0/0x438 lib/kobject.c:737
 put_device+0x28/0x40 drivers/base/core.c:3797
 put_disk+0x4c/0x64 block/genhd.c:1545
 loop_remove+0x9c/0xcc drivers/block/loop.c:2121
 loop_control_remove drivers/block/loop.c:2173 [inline]
 loop_control_ioctl+0x44c/0x514 drivers/block/loop.c:2211
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl fs/ioctl.c:584 [inline]
 __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:584
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x254 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

The buggy address belongs to the object at ffff0000c154b980
 which belongs to the cache bdev_cache of size 2808
The buggy address is located 56 bytes inside of
 freed 2808-byte region [ffff0000c154b980, ffff0000c154c478)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x101548
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x5ffc00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 05ffc00000000040 ffff0000c18be3c0 dead000000000122 0000000000000000
raw: 0000000000000000 00000000000b000b 00000000f5000000 0000000000000000
head: 05ffc00000000040 ffff0000c18be3c0 dead000000000122 0000000000000000
head: 0000000000000000 00000000000b000b 00000000f5000000 0000000000000000
head: 05ffc00000000003 fffffdffc3055201 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000c154b880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc
 ffff0000c154b900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000c154b980: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff0000c154ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000c154ba80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
bcachefs (loop0): shutting down
bcachefs (loop0): going read-only
bcachefs (loop0): finished waiting for writes to stop
bcachefs (loop0): flushing journal and stopping allocators, journal seq 18
bcachefs (loop0): flushing journal and stopping allocators complete, journal seq 18
bcachefs (loop0): insufficient writeable journal devices available: have 0, need 1
rw journal devs:
bcachefs (loop0): clean shutdown complete, journal seq 19
bcachefs (loop0): bch2_write_super(): fatal error : Unable to write superblock to sufficient devices (from bch2_fs_read_only)
bcachefs (loop0): done going read-only, filesystem not clean
bcachefs (loop0): shutdown complete