Seems a same bug on Ubuntu 20.04 kernel 5.4.0-52. The bug reproduces for me only under high load of CPU(for example, java compilation process)
---------------------
[10798.058030] bpfilter: Loaded bpfilter_umh pid 17193
[10798.058119] Started bpfilter
[14269.588116] BUG: unable to handle page fault for address: ffff919d84135500
[14269.588119] #PF: supervisor read access in kernel mode
[14269.588119] #PF: error_code(0x0000) - not-present page
[14269.588120] PGD 1f4c01067 P4D 1f4c01067 PUD 0 
[14269.588122] Oops: 0000 [#1] SMP NOPTI
[14269.588123] CPU: 5 PID: 21991 Comm: Chrome_ChildIOT Kdump: loaded Not tainted 5.4.0-52-generic #57-Ubuntu
[14269.588123] Hardware name: Gigabyte Technology Co., Ltd. B365M D3H/B365M D3H-CF, BIOS F3c 11/28/2019
[14269.588126] RIP: 0010:lock_page_memcg+0x1f/0x90
[14269.588127] Code: 0f 1f 84 00 00 00 00 00 0f 1f 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 53 0f 1f 44 00 00 48 89 fb 4c 8b 67 38 4d 85 e4 74 36 <41> 8b 84 24 00 05 00 00 85 c0 7e 2d 4d 8d ac 24 b8 04 00 00 4c 89
[14269.588128] RSP: 0018:ffffb6ca43047bc8 EFLAGS: 00010286
[14269.588129] RAX: ffffeaf69e86afc0 RBX: ffffeaf69e86afc0 RCX: 8000000000000005
[14269.588129] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffeaf69e86afc0
[14269.588130] RBP: ffffb6ca43047be0 R08: ffffeaf69e86afc0 R09: 0000000000000000
[14269.588130] R10: 0000000000000001 R11: ffff91bdaf7d5000 R12: ffff919d84135000
[14269.588131] R13: 000055986f674000 R14: 80000007a1abf005 R15: 000055986f675000
[14269.588132] FS:  00007f7768299700(0000) GS:ffff91bd8f340000(0000) knlGS:0000000000000000
[14269.588132] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[14269.588133] CR2: ffff919d84135500 CR3: 00000001f420a002 CR4: 00000000003606e0
[14269.588134] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[14269.588134] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[14269.588134] Call Trace:
[14269.588137]  page_remove_rmap+0xa5/0x310
[14269.588139]  ? tlb_flush_mmu+0x3a/0x140
[14269.588140]  zap_pte_range.isra.0+0x273/0x7f0
[14269.588141]  unmap_page_range+0x2da/0x4a0
[14269.588142]  unmap_single_vma+0x7f/0xf0
[14269.588143]  unmap_vmas+0x79/0xf0
[14269.588144]  exit_mmap+0xb4/0x1b0
[14269.588146]  mmput+0x5d/0x130
[14269.588147]  do_exit+0x306/0xac0
[14269.588148]  __x64_sys_exit+0x1b/0x20
[14269.588150]  do_syscall_64+0x57/0x190
[14269.588152]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[14269.588153] RIP: 0033:0x559870c0bee5
[14269.588155] Code: Bad RIP value.
[14269.588155] RSP: 002b:00007f77682979a0 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
[14269.588156] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000559870c0bee5
[14269.588156] RDX: 0000000000000001 RSI: 0000000000000009 RDI: 0000000000000000
[14269.588157] RBP: 00007f7768297d20 R08: 000000000000008c R09: 000000000000000e
[14269.588157] R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7768297d30
[14269.588158] R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000000
[14269.588159] Modules linked in: xt_tcpudp xt_state xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c ip6table_filter ip6_tables iptable_filter bpfilter cpuid snd_hda_codec_hdmi intel_rapl_msr intel_rapl_common x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm snd_hda_codec_realtek snd_hda_codec_generic ledtrig_audio mei_hdcp snd_hda_intel crct10dif_pclmul snd_intel_dspcfg ghash_clmulni_intel aesni_intel crypto_simd cryptd snd_hda_codec glue_helper rapl snd_hda_core intel_cstate snd_usb_audio snd_usbmidi_lib snd_hwdep mc snd_pcm nls_iso8859_1 snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq wmi_bmof i915 snd_seq_device snd_timer input_leds snd joydev soundcore drm_kms_helper i2c_algo_bit mei_me fb_sys_fops mei syscopyarea sysfillrect sysimgblt acpi_pad mac_hid acpi_tad sch_fq_codel parport_pc ppdev lp parport drm ip_tables x_tables autofs4 hid_generic usbhid hid crc32_pclmul nvme e1000e nvme_core i2c_i801 ahci libahci wmi video
[14269.588179] CR2: ffff919d84135500