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BUG: KASAN: slab-out-of-bounds in bch2_dirent_init_name+0x396/0x8b0
Write of size 1985 at addr ffff8881231ff041 by task syz.1.17/6020

CPU: 1 UID: 0 PID: 6020 Comm: syz.1.17 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+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 kasan_check_range+0x2b0/0x2c0
 __asan_memset+0x22/0x50
 bch2_dirent_init_name+0x396/0x8b0
 bch2_dirent_create_key+0x2a1/0x5f0
 bch2_dirent_create+0xc5/0xc80
 bch2_link_trans+0x39e/0x560
 __bch2_link+0x231/0x3f0
 bch2_link+0x197/0x220
 vfs_link+0x4ed/0x6e0
 do_linkat+0x272/0x560
 __x64_sys_linkat+0xd4/0xf0
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5b5458ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5b55458038 EFLAGS: 00000246 ORIG_RAX: 0000000000000109
RAX: ffffffffffffffda RBX: 00007f5b547c5fa0 RCX: 00007f5b5458ebe9
RDX: ffffffffffffff9c RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007f5b54611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 00002000000006c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5b547c6038 R14: 00007f5b547c5fa0 R15: 00007fff6928e6b8
 </TASK>

Allocated by task 6020:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_noprof+0x27a/0x4f0
 __bch2_trans_kmalloc+0x396/0x9d0
 bch2_dirent_create_key+0x113/0x5f0
 bch2_dirent_create+0xc5/0xc80
 bch2_link_trans+0x39e/0x560
 __bch2_link+0x231/0x3f0
 bch2_link+0x197/0x220
 vfs_link+0x4ed/0x6e0
 do_linkat+0x272/0x560
 __x64_sys_linkat+0xd4/0xf0
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8881231ff000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 65 bytes inside of
 allocated 2048-byte region [ffff8881231ff000, ffff8881231ff800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1231f8
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff88801a442000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff88801a442000 dead000000000100 dead000000000122
head: 0000000000000000 0000000080080008 00000000f5000000 0000000000000000
head: 057ff00000000003 ffffea00048c7e01 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 5858, tgid 5858 (syz-executor), ts 65093911663, free_ts 0
 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/0x370
 ___slab_alloc+0xbeb/0x1410
 __kmalloc_node_noprof+0x2fd/0x4e0
 qdisc_alloc+0x97/0xaa0
 qdisc_create_dflt+0x8e/0x4e0
 dev_activate+0x378/0x1150
 __dev_open+0x69c/0x880
 __dev_change_flags+0x1ea/0x6d0
 netif_change_flags+0x88/0x1a0
 do_setlink+0xc55/0x41c0
 rtnl_newlink+0x160b/0x1c70
 rtnetlink_rcv_msg+0x7cf/0xb70
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8881231ff700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881231ff780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881231ff800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff8881231ff880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881231ff900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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