kernel BUG at mm/huge_memory.c:LINE!

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    4cd1b60def51 Add linux-next specific files for 20190102
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=147760d3400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e8ea56601353001c
dashboard link: https://syzkaller.appspot.com/bug?extid=8e075128f7db8555391a
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8e075128f7db8555391a@xxxxxxxxxxxxxxxxxxxxxxxxx

raw: 01fffc000009000d dead000000000100 dead000000000200 ffff88809a33f5b1
raw: 0000000000020000 0000000000000000 0000020000000000 ffff888095368000
page dumped because: VM_BUG_ON_PAGE(compound_mapcount(head))
page->mem_cgroup:ffff888095368000
------------[ cut here ]------------
kernel BUG at mm/huge_memory.c:2683!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 1551 Comm: kswapd0 Not tainted 4.20.0-next-20190102 #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:split_huge_page_to_list+0x2161/0x2ac0 mm/huge_memory.c:2683
Code: ff e8 33 35 b8 ff 48 8b 85 10 fc ff ff 4c 8d 70 ff e9 1e ea ff ff e8  
1e 35 b8 ff 48 c7 c6 a0 a3 54 88 4c 89 ef e8 0f 15 ea ff <0f> 0b 48 89 85  
10 fc ff ff e8 01 35 b8 ff 48 8b 85 10 fc ff ff 4c
RSP: 0018:ffff8880a5f36de8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8880a5f371d8 RCX: 0000000000000000
RDX: ffffed1014be6d6e RSI: ffffffff81b3831e RDI: ffffed1014be6dae
RBP: ffff8880a5f37200 R08: 0000000000000021 R09: ffffed1015cc5021
R10: ffffed1015cc5020 R11: ffff8880ae628107 R12: ffffea0000e80080
R13: ffffea0000e80000 R14: 00000000fffffffe R15: 01fffc000009000d
FS:  0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020003030 CR3: 0000000219267000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 split_huge_page include/linux/huge_mm.h:148 [inline]
 deferred_split_scan+0xa47/0x11d0 mm/huge_memory.c:2820
 do_shrink_slab+0x4e5/0xd30 mm/vmscan.c:561
 shrink_slab mm/vmscan.c:710 [inline]
 shrink_slab+0x6bb/0x8c0 mm/vmscan.c:690
 shrink_node+0x61a/0x17e0 mm/vmscan.c:2776
 kswapd_shrink_node mm/vmscan.c:3535 [inline]
 balance_pgdat+0xb00/0x18b0 mm/vmscan.c:3693
 kswapd+0x839/0x1330 mm/vmscan.c:3948
 kthread+0x357/0x430 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Modules linked in:
kobject: 'loop1' (000000002d2ad2ad): kobject_uevent_env
kobject: 'loop1' (000000002d2ad2ad): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
kobject: 'loop3' (000000003c94a079): kobject_uevent_env
kobject: 'loop3' (000000003c94a079): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
kobject: 'loop5' (0000000000e89d9d): kobject_uevent_env
kobject: 'loop5' (0000000000e89d9d): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
kobject: 'loop2' (000000001a685ee7): kobject_uevent_env
kobject: 'loop2' (000000001a685ee7): fill_kobj_path: path  
= '/devices/virtual/block/loop2'
kobject: 'loop3' (000000003c94a079): kobject_uevent_env
kobject: 'loop3' (000000003c94a079): fill_kobj_path: path  
= '/devices/virtual/block/loop3'
---[ end trace a543f5c1741fca97 ]---
kobject: 'loop0' (00000000aa59ea1f): kobject_uevent_env
RIP: 0010:split_huge_page_to_list+0x2161/0x2ac0 mm/huge_memory.c:2683
Code: ff e8 33 35 b8 ff 48 8b 85 10 fc ff ff 4c 8d 70 ff e9 1e ea ff ff e8  
1e 35 b8 ff 48 c7 c6 a0 a3 54 88 4c 89 ef e8 0f 15 ea ff <0f> 0b 48 89 85  
10 fc ff ff e8 01 35 b8 ff 48 8b 85 10 fc ff ff 4c
kobject: 'loop0' (00000000aa59ea1f): fill_kobj_path: path  
= '/devices/virtual/block/loop0'
RSP: 0018:ffff8880a5f36de8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8880a5f371d8 RCX: 0000000000000000
RDX: ffffed1014be6d6e RSI: ffffffff81b3831e RDI: ffffed1014be6dae
RBP: ffff8880a5f37200 R08: 0000000000000021 R09: ffffed1015cc5021
netlink: 'syz-executor0': attribute type 22 has an invalid length.
R10: ffffed1015cc5020 R11: ffff8880ae628107 R12: ffffea0000e80080
R13: ffffea0000e80000 R14: 00000000fffffffe R15: 01fffc000009000d
FS:  0000000000000000(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
kobject: 'loop1' (000000002d2ad2ad): kobject_uevent_env
kobject: 'loop1' (000000002d2ad2ad): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004efb18 CR3: 00000000702a7000 CR4: 00000000001426e0
kobject: 'loop5' (0000000000e89d9d): kobject_uevent_env
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
kobject: 'loop5' (0000000000e89d9d): fill_kobj_path: path  
= '/devices/virtual/block/loop5'
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
kobject: 'loop3' (000000003c94a079): kobject_uevent_env


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