BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
PGD 0 P4D 0 
Oops: 0000 [#1] SMP PTI
CPU: 1 PID: 4767 Comm: syz-fuzzer Not tainted 4.19.0-rc1+ #40
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:kmsan_free_page+0xec/0x2d0 mm/kmsan/kmsan_hooks.c:318
Code: 01 00 00 48 c7 00 00 00 00 00 44 39 e1 0f 8d b0 00 00 00 48 63 d1 48 8d 14 52 48 c1 e2 05 48 8b 54 13 40 48 83 c0 60 83 c1 01 <80> 7a 50 00 74 be 0f 0b 66 90 66 2e 0f 1f 84 00 00 00 00 00 eb fe
RSP: 0018:ffff8801bfa8ef80 EFLAGS: 00010006
RAX: ffffea0009a3f548 RBX: ffffea0009a38000 RCX: 0000000000000139
RDX: 0000000000000000 RSI: 0000000000000009 RDI: ffffea00004e0000
RBP: ffff8801bfa8efc8 R08: 0000000000480020 R09: 0000000000000002
R10: 0000000000000000 R11: ffffffff81c45470 R12: 0000000000000200
R13: ffff88019c113b00 R14: 0000000000000009 R15: ffffea00004ec000
FS:  000000c420088e68(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000050 CR3: 0000000009c30000 CR4: 00000000001406e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 free_pages_prepare mm/page_alloc.c:994 [inline]
 __free_pages_ok+0x25a/0x16c0 mm/page_alloc.c:1252
 free_compound_page+0x8b/0xc0 mm/page_alloc.c:572
 free_transhuge_page+0x3af/0x460 mm/huge_memory.c:2733
 __put_compound_page mm/swap.c:96 [inline]
 release_pages+0x70c/0x1650 mm/swap.c:760
 free_pages_and_swap_cache+0x54b/0x570 mm/swap_state.c:319
 tlb_flush_mmu_free mm/memory.c:250 [inline]
 zap_pte_range mm/memory.c:1406 [inline]
 zap_pmd_range mm/memory.c:1441 [inline]
 zap_pud_range mm/memory.c:1470 [inline]
 zap_p4d_range mm/memory.c:1491 [inline]
 unmap_page_range+0x37b8/0x4170 mm/memory.c:1512
 unmap_single_vma+0x445/0x5e0 mm/memory.c:1557
 unmap_vmas+0x251/0x380 mm/memory.c:1587
 exit_mmap+0x4b7/0x940 mm/mmap.c:3093
 __mmput+0x154/0x5f0 kernel/fork.c:1003
 mmput+0xa7/0xe0 kernel/fork.c:1024
 exit_mm+0x6dd/0x790 kernel/exit.c:546
 do_exit+0xbf7/0x3890 kernel/exit.c:856
 do_group_exit+0x1a0/0x350 kernel/exit.c:972
 get_signal+0x1425/0x1ef0 kernel/signal.c:2513
 do_signal+0x11d/0x2060 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop arch/x86/entry/common.c:162 [inline]
 prepare_exit_to_usermode+0x273/0x410 arch/x86/entry/common.c:197
 retint_user+0x8/0x8
RIP: 0033:0x5e6bc0
Code: Bad RIP value.
RSP: 002b:000000c42c121bd8 EFLAGS: 00010202
RAX: 0000000000000003 RBX: 0000000000000001 RCX: 000000c42006d680
RDX: 000000c42c121d50 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 000000c42c121c08 R08: 0000000000000008 R09: 0000000000000010
R10: 000000c42b5b7490 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000018 R14: 0000000000000011 R15: 0000000000000018
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
CR2: 0000000000000050
---[ end trace 9075d75c7233c70d ]---
RIP: 0010:kmsan_free_page+0xec/0x2d0 mm/kmsan/kmsan_hooks.c:318
Code: 01 00 00 48 c7 00 00 00 00 00 44 39 e1 0f 8d b0 00 00 00 48 63 d1 48 8d 14 52 48 c1 e2 05 48 8b 54 13 40 48 83 c0 60 83 c1 01 <80> 7a 50 00 74 be 0f 0b 66 90 66 2e 0f 1f 84 00 00 00 00 00 eb fe
RSP: 0018:ffff8801bfa8ef80 EFLAGS: 00010006
RAX: ffffea0009a3f548 RBX: ffffea0009a38000 RCX: 0000000000000139
RDX: 0000000000000000 RSI: 0000000000000009 RDI: ffffea00004e0000
RBP: ffff8801bfa8efc8 R08: 0000000000480020 R09: 0000000000000002
R10: 0000000000000000 R11: ffffffff81c45470 R12: 0000000000000200
R13: ffff88019c113b00 R14: 0000000000000009 R15: ffffea00004ec000
FS:  000000c420088e68(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000005e6b96 CR3: 0000000009c30000 CR4: 00000000001406e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600