kAFS: unable to lookup cell ''
==================================================================
BUG: KASAN: slab-use-after-free in string+0x216/0x2d0
Read of size 1 at addr ffff88816b281260 by task syz.1.995/14121

CPU: 1 UID: 0 PID: 14121 Comm: syz.1.995 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: 0033:0x7fb19979e159
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:00007fb19a708028 EFLAGS: 00000246 ORIG_RAX: 0000000000000008
RAX: ffffffffffffffda RBX: 00007fb199a26090 RCX: 00007fb19979e159
RDX: 0000000000000000 RSI: 0000002000000008 RDI: 000000000000000b
RBP: 00007fb19983506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb199a26128 R14: 00007fb199a26090 R15: 00007ffc24079de8
 </TASK>

Allocated by task 13176:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_node_noprof+0x4b9/0x720
 __vmalloc_node_range_noprof+0x5b4/0x1540
 vzalloc_noprof+0xb2/0xe0
 alloc_counters+0x63/0x5d0
 do_ip6t_get_ctl+0xb17/0x12f0
 nf_getsockopt+0x26e/0x290
 ipv6_getsockopt+0x213/0x2c0
 do_sock_getsockopt+0x51d/0x7e0
 __x64_sys_getsockopt+0x1a4/0x240
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 13176:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x40/0x50
 __kasan_slab_free+0x5c/0x80
 kfree+0x1c5/0x650
 vfree+0x42b/0x490
 do_ip6t_get_ctl+0xf3e/0x12f0
 nf_getsockopt+0x26e/0x290
 ipv6_getsockopt+0x213/0x2c0
 do_sock_getsockopt+0x51d/0x7e0
 __x64_sys_getsockopt+0x1a4/0x240
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88816b281260
 which belongs to the cache kmalloc-8 of size 8
The buggy address is located 0 bytes inside of
 freed 8-byte region [ffff88816b281260, ffff88816b281268)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88816b281b80 pfn:0x16b281
flags: 0x57ff00000000200(workingset|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000200 ffff888100041500 ffffea0005a58e50 ffffea0005b8db10
raw: ffff88816b281b80 0000000000800068 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 5402180924
 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_create_dir_ns+0xfe/0x230
 sysfs_create_dir_ns+0x12f/0x2a0
 kobject_add_internal+0x622/0xcd0
 kobject_add+0x163/0x240
 device_add+0x3fa/0xb80
 tty_register_device_attr+0x425/0x990
 tty_register_driver+0x868/0xe50
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88816b281100: fa fc fc fc fa fc fc fc 06 fc fc fc fa fc fc fc
 ffff88816b281180: 06 fc fc fc 06 fc fc fc 06 fc fc fc fa fc fc fc
>ffff88816b281200: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
                                                       ^
 ffff88816b281280: fa fc fc fc fa fc fc fc 00 fc fc fc fa fc fc fc
 ffff88816b281300: 00 fc fc fc fa fc fc fc fa fc fc fc 04 fc fc fc
==================================================================
