kernel BUG at include/linux/mm.h:519!

[Qian Cai]

Running the trinity fuzzer with a non-root user on an aarch64 server with the
latest mainline (rc2) triggered this,

[ 2058.662628] page:ffff7fe022fe7d80 count:0 mapcount:0 mapping:ffff808ea6153160
index:0x5a
[ 2058.670842] flags: 0x9fffff0000000004(uptodate)
[ 2058.675448] raw: 9fffff0000000004 dead000000000100 dead000000000200
0000000000000000
[ 2058.683254] raw: 000000000000005a 0000000000000000 00000001ffffffff
ffff801ec3d67680
[ 2058.691004] page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
[ 2058.697954] page->mem_cgroup:ffff801ec3d67680
[ 2058.702355] ------------[ cut here ]------------
[ 2058.706974] kernel BUG at include/linux/mm.h:519!
[ 2058.711964] Internal error: Oops - BUG: 0 [#1] SMP
[ 2058.711966] irq event stamp: 223221
[ 2058.711972] irq event stamp: 466900
[ 2058.711976] irq event stamp: 124299
[ 2058.711990] hardirqs lastÂÂenabled at (223221): [<ffff2000080839fc>]
el1_irq+0xbc/0x140
[ 2058.712014] hardirqs lastÂÂenabled at (466899): [<ffff200008280500>]
tick_nohz_idle_exit+0x80/0xf0
[ 2058.712022] hardirqs lastÂÂenabled at (124299): [<ffff2000080839fc>]
el1_irq+0xbc/0x140
[ 2058.712031] hardirqs last disabled at (466900): [<ffff200008f9e0e4>]
__schedule+0x1d4/0xda0
[ 2058.712036] hardirqs last disabled at (124298): [<ffff2000080839b4>]
el1_irq+0x74/0x140
[ 2058.712046] softirqs lastÂÂenabled at (466894): [<ffff20000812cf5c>]
_local_bh_enable+0xb4/0xf0
[ 2058.712051] softirqs lastÂÂenabled at (124290): [<ffff200008082210>]
__do_softirq+0x7c8/0x9c8
[ 2058.712057] softirqs last disabled at (466893): [<ffff20000812d968>]
irq_enter+0x128/0x148
[ 2058.712065] softirqs last disabled at (124283): [<ffff20000812dbe4>]
irq_exit+0x25c/0x2f0
[ 2058.716762] Modules linked in: 8021q garp mrp af_key dlci bridge stp llc pptp
gre l2tp_ppp l2tp_netlink l2tp_core ip6_udp_tunnel udp_tunnel pppoe pppox
ppp_generic slhc crypto_user ib_core nfnetlink scsi_transport_iscsi atm sctp
vfat fat ghash_ce sha2_ce sha256_arm64 sha1_ce ses enclosure ipmi_ssif sg
ipmi_si ipmi_devintf sbsa_gwdt ipmi_msghandler sch_fq_codel xfs libcrc32c
marvell mpt3sas raid_class mlx5_core hibmc_drm drm_kms_helper syscopyarea
sysfillrect sysimgblt fb_sys_fops ttm drm ixgbe hisi_sas_v2_hw igb hisi_sas_main
libsas hns_dsaf mlxfw hns_enet_drv devlink i2c_designware_platform mdio
i2c_algo_bit ehci_platform scsi_transport_sas i2c_designware_core hns_mdio hnae
dm_mirror dm_region_hash dm_log dm_mod
[ 2058.720243] hardirqs last disabled at (223220): [<ffff2000080839b4>]
el1_irq+0x74/0x140
[ 2058.723721] CPU: 9 PID: 14438 Comm: trinity-c248 Kdump: loaded Tainted:
GÂÂÂÂÂÂÂÂWÂÂÂÂÂÂÂÂÂ4.20.0-rc2+ #16
[ 2058.727197] softirqs lastÂÂenabled at (223218): [<ffff200008082210>]
__do_softirq+0x7c8/0x9c8
[ 2058.727205] softirqs last disabled at (223209): [<ffff20000812dbe4>]
irq_exit+0x25c/0x2f0
[ 2058.735193] Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.50
06/01/2018
[ 2058.906697] pstate: 20000005 (nzCv daif -PAN -UAO)
[ 2058.911487] pc : release_pages+0xa40/0xfa0
[ 2058.915578] lr : release_pages+0xa40/0xfa0
[ 2058.919667] sp : ffff801e7020e610
[ 2058.922975] x29: ffff801e7020e610 x28: 1ffff003ce041ce6Â
[ 2058.928283] x27: ffff1003ce041cf6 x26: 0000000000000000Â
[ 2058.933591] x25: ffff801e7020f328 x24: ffff801e7020e770Â
[ 2058.938898] x23: ffff20000a103630 x22: 00000000fffffff8Â
[ 2058.944206] x21: ffff80163deb0278 x20: dfff200000000000Â
[ 2058.949513] x19: ffff7fe022fe7d80 x18: 0000000000000000Â
[ 2058.954821] x17: 0000000000000000 x16: 0000000000000000Â
[ 2058.960127] x15: 0000000000000000 x14: 6531303866666666Â
[ 2058.965434] x13: 2066666666666666 x12: ffff04000172b58eÂ
[ 2058.970741] x11: 00000000f2f2f2f2 x10: dfff200000000000Â
[ 2058.976049] x9 : ffff20000a0f9848 x8 : ffff808d0319da88Â
[ 2058.981356] x7 : 00000000f2f2f204 x6 : 0000000041b58ab3Â
[ 2058.986663] x5 : ffff1003ce041b5c x4 : dfff200000000000Â
[ 2058.991970] x3 : dfff200000000000 x2 : 65a2459128144800Â
[ 2058.997278] x1 : 65a2459128144800 x0 : 0000000000000000Â
[ 2059.002588] Process trinity-c248 (pid: 14438, stack limit =
0x0000000037b8b477)
[ 2059.009889] Call trace:
[ 2059.012331]ÂÂrelease_pages+0xa40/0xfa0
[ 2059.016077]ÂÂfree_pages_and_swap_cache+0x258/0x320
[ 2059.020862]ÂÂtlb_flush_mmu_free+0x5c/0xa0
[ 2059.024866]ÂÂtlb_flush_mmu+0x280/0x418
[ 2059.028610]ÂÂarch_tlb_finish_mmu+0xbc/0x138
[ 2059.032787]ÂÂtlb_finish_mmu+0xd4/0x120
[ 2059.036531]ÂÂexit_mmap+0x1c4/0x260
[ 2059.039928]ÂÂmmput+0x154/0x310
[ 2059.042977]ÂÂdo_exit+0x7ec/0xd70
[ 2059.046200]ÂÂdo_group_exit+0xc4/0x180
[ 2059.049857]ÂÂget_signal+0x544/0xce0
[ 2059.053341]ÂÂdo_signal+0x104/0x358
[ 2059.056738]ÂÂdo_notify_resume+0x19c/0x200
[ 2059.060741]ÂÂwork_pending+0x8/0x14
[ 2059.064140] Code: 91000021 aa1303e0 911f8021 94015f13 (d4210000)Â
[ 2059.070371] SMP: stopping secondary CPUs
[ 2059.078701] Starting crashdump kernel...
[ 2059.082625] Bye!