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BUG: KASAN: slab-use-after-free in bch2_get_next_dev+0x371/0x4c0
Write of size 8 at addr ffff888048f86040 by task kworker/u12:1/6013

CPU: 0 UID: 0 PID: 6013 Comm: kworker/u12:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: bcachefs_journal journal_write_done
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 kasan_check_range+0x2b0/0x2c0
 bch2_get_next_dev+0x371/0x4c0
 bch2_do_discards+0x20/0x160
 journal_write_done+0x119a/0x13d0
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x47f/0x820
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 13873:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x3d5/0x6f0
 __bch2_dev_alloc+0xa7/0xc30
 bch2_dev_alloc+0xcd/0x180
 bch2_fs_open+0x2477/0x2600
 bch2_fs_get_tree+0x44f/0x1520
 vfs_get_tree+0x92/0x2b0
 do_new_mount+0x302/0xa10
 __se_sys_mount+0x313/0x410
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 13873:
 kasan_save_track+0x3e/0x80
 __kasan_save_free_info+0x46/0x50
 __kasan_slab_free+0x5b/0x80
 kfree+0x199/0x6d0
 kobject_put+0x22b/0x480
 bch2_fs_free+0x440/0x5a0
 bch2_fs_get_tree+0xb6e/0x1520
 vfs_get_tree+0x92/0x2b0
 do_new_mount+0x302/0xa10
 __se_sys_mount+0x313/0x410
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888048f86000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 64 bytes inside of
 freed 4096-byte region [ffff888048f86000, ffff888048f87000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x48f80
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 ffff88801a842140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801a842140 dead000000000122 0000000000000000
head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea000123e001 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 29, tgid 29 (kworker/u9:1), ts 702854933362, free_ts 702069253594
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x8a/0x330
 ___slab_alloc+0xbd1/0x13f0
 __slab_alloc+0x55/0xa0
 __kmalloc_node_track_caller_noprof+0x5c7/0x800
 kmalloc_reserve+0x136/0x290
 __alloc_skb+0x142/0x2d0
 nsim_dev_trap_report_work+0x29a/0xb80
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x47f/0x820
 ret_from_fork_asm+0x1a/0x30
page last free pid 13880 tgid 13879 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __put_partials+0x146/0x170
 put_cpu_partial+0x17c/0x250
 __slab_free+0x2b9/0x390
 qlist_free_all+0x97/0x140
 kasan_quarantine_reduce+0x148/0x160
 __kasan_slab_alloc+0x22/0x80
 kmem_cache_alloc_noprof+0x367/0x6e0
 alloc_empty_file+0x55/0x1d0
 path_openat+0x107/0x3830
 do_filp_open+0x1fa/0x410
 do_sys_openat2+0x121/0x1c0
 __x64_sys_openat+0x138/0x170
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888048f85f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888048f85f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888048f86000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff888048f86080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888048f86100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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