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BUG: KASAN: slab-use-after-free in string+0x216/0x2d0
Read of size 1 at addr ffff88816c2569a0 by task syz.3.2335/11981

CPU: 0 UID: 0 PID: 11981 Comm: syz.3.2335 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
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_address_description+0x55/0x1e0
 print_report+0x58/0x70
 kasan_report+0x117/0x150
 string+0x216/0x2d0
 vsnprintf+0x74a/0xef0
 seq_printf+0x188/0x290
 irq_seq_show+0x5f3/0x860
 traverse+0x229/0x620
 seq_lseek+0x134/0x260
 proc_reg_llseek+0x1bc/0x290
 __x64_sys_lseek+0x14f/0x1e0
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6b7799e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6b787fa028 EFLAGS: 00000246 ORIG_RAX: 0000000000000008
RAX: ffffffffffffffda RBX: 00007f6b77c25fa0 RCX: 00007f6b7799e159
RDX: 0000000000000001 RSI: 7fffffffffffffff RDI: 0000000000000003
RBP: 00007f6b77a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6b77c26038 R14: 00007f6b77c25fa0 R15: 00007ffd6de3d2e8
 </TASK>

Allocated by task 11643:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_node_track_caller_noprof+0x4b4/0x720
 kstrdup+0x42/0x100
 __kernfs_new_node+0xa9/0x980
 kernfs_create_dir_ns+0xfe/0x230
 sysfs_create_dir_ns+0x12f/0x2a0
 kobject_add_internal+0x622/0xcd0
 kobject_init_and_add+0x12b/0x1a0
 ext4_register_sysfs+0xc0/0x2d0
 ext4_fill_super+0x60a4/0x6610
 get_tree_bdev_flags+0x430/0x4f0
 vfs_get_tree+0x92/0x2a0
 do_new_mount+0x319/0xdc0
 __se_sys_mount+0x31d/0x420
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 9992:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x40/0x50
 __kasan_slab_free+0x5c/0x80
 kfree+0x1c5/0x650
 kernfs_free_rcu+0x3b/0xd0
 rcu_core+0x926/0x1260
 handle_softirqs+0x226/0x860
 __irq_exit_rcu+0xcb/0x220
 irq_exit_rcu+0x9/0x30
 sysvec_apic_timer_interrupt+0xa6/0xc0
 asm_sysvec_apic_timer_interrupt+0x1a/0x20

The buggy address belongs to the object at ffff88816c2569a0
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 freed 8-byte region [ffff88816c2569a0, ffff88816c2569a8)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88816c256980 pfn:0x16c256
flags: 0x57ff00000000200(workingset|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000200 ffff888100041500 ffffea000598c390 ffffea000596d290
raw: ffff88816c256980 0000000000800072 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 5174218403
 post_alloc_hook+0x1f9/0x250
 get_page_from_freelist+0x2209/0x2280
 __alloc_frozen_pages_noprof+0x217/0x5a0
 allocate_slab+0x7d/0x620
 refill_objects+0x2d5/0x350
 __pcs_replace_empty_main+0x2c8/0x6c0
 __kmalloc_node_track_caller_noprof+0x548/0x720
 kstrdup+0x42/0x100
 __kernfs_new_node+0xa9/0x980
 kernfs_new_node+0xea/0x140
 kernfs_create_link+0xa7/0x200
 sysfs_do_create_link_sd+0x83/0x110
 device_create_sys_dev_entry+0x122/0x190
 device_add+0x71e/0xb80
 tty_register_device_attr+0x425/0x990
 tty_register_driver+0x868/0xe50
page last free pid 53 tgid 53 ts 5173726511 stack trace:
 __free_frozen_pages+0xc93/0xd90
 __kasan_populate_vmalloc+0x1a8/0x1c0
 alloc_vmap_area+0xd1a/0x1420
 __get_vm_area_node+0x200/0x2f0
 __vmalloc_node_range_noprof+0x343/0x1540
 __vmalloc_node_noprof+0xc2/0x100
 dup_task_struct+0x2c6/0xa00
 copy_process+0x7e0/0x4400
 kernel_clone+0x2d7/0x940
 user_mode_thread+0x115/0x180
 call_usermodehelper_exec_work+0x5c/0x230
 process_scheduled_works+0xc3d/0x1630
 worker_thread+0xa47/0xfb0
 kthread+0x38b/0x480
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30

Memory state around the buggy address:
 ffff88816c256880: 06 fc fc fc fa fc fc fc 06 fc fc fc 06 fc fc fc
 ffff88816c256900: 06 fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
>ffff88816c256980: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
                               ^
 ffff88816c256a00: 00 fc fc fc fa fc fc fc 00 fc fc fc fa fc fc fc
 ffff88816c256a80: fa fc fc fc 04 fc fc fc 00 fc fc fc 00 fc fc fc
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