==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_long_inc_return include/linux/atomic/atomic-instrumented.h:3609 [inline]
BUG: KASAN: slab-use-after-free in bch2_dev_get fs/bcachefs/sb-members.h:114 [inline]
BUG: KASAN: slab-use-after-free in bch2_get_next_dev fs/bcachefs/sb-members.h:145 [inline]
BUG: KASAN: slab-use-after-free in bch2_do_discards+0x319/0x570 fs/bcachefs/alloc_background.c:1984
Write of size 8 at addr ffff8880326ca040 by task kworker/u9:7/5886

CPU: 0 UID: 0 PID: 5886 Comm: kworker/u9:7 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: bcachefs_journal journal_write_done
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xcd/0x630 mm/kasan/report.c:482
 kasan_report+0xe0/0x110 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_long_inc_return include/linux/atomic/atomic-instrumented.h:3609 [inline]
 bch2_dev_get fs/bcachefs/sb-members.h:114 [inline]
 bch2_get_next_dev fs/bcachefs/sb-members.h:145 [inline]
 bch2_do_discards+0x319/0x570 fs/bcachefs/alloc_background.c:1984
 journal_write_done+0xee4/0x1430 fs/bcachefs/journal_io.c:1821
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3236
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6371:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 __bch2_dev_alloc+0xb5/0xff0 fs/bcachefs/super.c:1487
 bch2_dev_alloc+0xb8/0x190 fs/bcachefs/super.c:1558
 bch2_fs_alloc+0x19ca/0x23f0 fs/bcachefs/super.c:1051
 bch2_fs_open+0x838/0xc50 fs/bcachefs/super.c:2433
 bch2_fs_get_tree+0xcb0/0x1b70 fs/bcachefs/fs.c:2472
 vfs_get_tree+0x8e/0x340 fs/super.c:1815
 do_new_mount fs/namespace.c:3808 [inline]
 path_mount+0x1513/0x2000 fs/namespace.c:4123
 do_mount fs/namespace.c:4136 [inline]
 __do_sys_mount fs/namespace.c:4347 [inline]
 __se_sys_mount fs/namespace.c:4324 [inline]
 __x64_sys_mount+0x28d/0x310 fs/namespace.c:4324
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6371:
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x60/0x70 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]
 kfree+0x2b4/0x4d0 mm/slub.c:4894
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1e7/0x5a0 lib/kobject.c:737
 bch2_fs_free+0x225/0x420 fs/bcachefs/super.c:728
 bch2_fs_get_tree+0xd5e/0x1b70 fs/bcachefs/fs.c:2604
 vfs_get_tree+0x8e/0x340 fs/super.c:1815
 do_new_mount fs/namespace.c:3808 [inline]
 path_mount+0x1513/0x2000 fs/namespace.c:4123
 do_mount fs/namespace.c:4136 [inline]
 __do_sys_mount fs/namespace.c:4347 [inline]
 __se_sys_mount fs/namespace.c:4324 [inline]
 __x64_sys_mount+0x28d/0x310 fs/namespace.c:4324
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880326ca000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 64 bytes inside of
 freed 4096-byte region [ffff8880326ca000, ffff8880326cb000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x326c8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b842140 ffffea0001eb7a00 dead000000000002
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b842140 ffffea0001eb7a00 dead000000000002
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0000c9b201 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
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 33478751455, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x132b/0x38e0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:5148
 alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2492 [inline]
 allocate_slab mm/slub.c:2660 [inline]
 new_slab+0x247/0x330 mm/slub.c:2714
 ___slab_alloc+0xcf2/0x1750 mm/slub.c:3901
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3992
 __slab_alloc_node mm/slub.c:4067 [inline]
 slab_alloc_node mm/slub.c:4228 [inline]
 __kmalloc_cache_noprof+0xfb/0x3e0 mm/slub.c:4402
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 kobject_uevent_env+0x265/0x1870 lib/kobject_uevent.c:540
 kernel_add_sysfs_param kernel/params.c:816 [inline]
 param_sysfs_builtin kernel/params.c:851 [inline]
 param_sysfs_builtin_init+0x367/0x4c0 kernel/params.c:987
 do_one_initcall+0x123/0x6e0 init/main.c:1269
 do_initcall_level init/main.c:1331 [inline]
 do_initcalls init/main.c:1347 [inline]
 do_basic_setup init/main.c:1366 [inline]
 kernel_init_freeable+0x5c2/0x910 init/main.c:1579
 kernel_init+0x1c/0x2b0 init/main.c:1469
 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880326c9f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880326c9f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880326ca000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff8880326ca080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880326ca100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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