BUG: Bad page state (6)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    42fd8df9d1d9 Add linux-next specific files for 20190228
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=179ba9e0c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c0f38652d28b522f
dashboard link: https://syzkaller.appspot.com/bug?extid=6f5a9b79b75b66078bf0
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12ed6bd0c00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10690c8ac00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6f5a9b79b75b66078bf0@xxxxxxxxxxxxxxxxxxxxxxxxx

BUG: Bad page state in process syz-executor193  pfn:9225a
page:ffffea0002489680 count:0 mapcount:0 mapping:ffff88808652fd80 index:0x81
shmem_aops
name:"memfd:cgroup2"
flags: 0x1fffc000008000e(referenced|uptodate|dirty|swapbacked)
raw: 01fffc000008000e ffff88809277fac0 ffff88809277fac0 ffff88808652fd80
raw: 0000000000000081 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: non-NULL mapping
Modules linked in:
CPU: 0 PID: 7659 Comm: syz-executor193 Not tainted 5.0.0-rc8-next-20190228  
#45
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 bad_page.cold+0xda/0xff mm/page_alloc.c:586
 free_pages_check_bad+0x142/0x1a0 mm/page_alloc.c:1013
 free_pages_check mm/page_alloc.c:1022 [inline]
 free_pages_prepare mm/page_alloc.c:1112 [inline]
 free_pcp_prepare mm/page_alloc.c:1137 [inline]
 free_unref_page_prepare mm/page_alloc.c:3001 [inline]
 free_unref_page_list+0x31d/0xc40 mm/page_alloc.c:3070
 release_pages+0x60d/0x1940 mm/swap.c:794
 pagevec_lru_move_fn+0x218/0x2a0 mm/swap.c:213
 activate_page_drain mm/swap.c:297 [inline]
 lru_add_drain_cpu+0x3b1/0x520 mm/swap.c:596
 lru_add_drain+0x20/0x60 mm/swap.c:647
 exit_mmap+0x290/0x530 mm/mmap.c:3134
 __mmput kernel/fork.c:1047 [inline]
 mmput+0x15f/0x4c0 kernel/fork.c:1068
 exit_mm kernel/exit.c:546 [inline]
 do_exit+0x816/0x2fa0 kernel/exit.c:863
 do_group_exit+0x135/0x370 kernel/exit.c:980
 __do_sys_exit_group kernel/exit.c:991 [inline]
 __se_sys_exit_group kernel/exit.c:989 [inline]
 __x64_sys_exit_group+0x44/0x50 kernel/exit.c:989
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x442a58
Code: 00 00 be 3c 00 00 00 eb 19 66 0f 1f 84 00 00 00 00 00 48 89 d7 89 f0  
0f 05 48 3d 00 f0 ff ff 77 21 f4 48 89 d7 44 89 c0 0f 05 <48> 3d 00 f0 ff  
ff 76 e0 f7 d8 64 41 89 01 eb d8 0f 1f 84 00 00 00
RSP: 002b:00007ffe99e2faf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000442a58
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004c2468 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000002000005 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d4180 R14: 0000000000000000 R15: 0000000000000000


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