BUG: unable to handle kernel NULL pointer dereference at 0000000000000050
PGD 0 P4D 0 
Oops: 0000 [#1] SMP PTI
CPU: 1 PID: 4495 Comm: syz-fuzzer Not tainted 4.18.0-rc8+ #34
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:ffff8801a662ee00 EFLAGS: 00010006
RAX: ffffea00034bea48 RBX: ffffea00034bc000 RCX: 0000000000000071
RDX: 0000000000000000 RSI: 0000000000000009 RDI: ffffea0003984000
RBP: ffff8801a662ee48 R08: 0000000000480020 R09: 0000000000000002
R10: 0000000000000000 R11: ffffffff81c1cc50 R12: 0000000000000200
R13: ffff8801c672d880 R14: 0000000000000009 R15: ffffea0003aa4000
FS:  000000c420028e68(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000050 CR3: 0000000009830000 CR4: 00000000001406e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
 free_pages_prepare mm/page_alloc.c:993 [inline]
 __free_pages_ok+0x25a/0x16c0 mm/page_alloc.c:1251
 free_compound_page+0x8b/0xc0 mm/page_alloc.c:571
 free_transhuge_page+0x3af/0x460 mm/huge_memory.c:2731
 __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:260 [inline]
 zap_pte_range mm/memory.c:1401 [inline]
 zap_pmd_range mm/memory.c:1436 [inline]
 zap_pud_range mm/memory.c:1465 [inline]
 zap_p4d_range mm/memory.c:1486 [inline]
 unmap_page_range+0x34a8/0x3b60 mm/memory.c:1507
 unmap_single_vma+0x445/0x5e0 mm/memory.c:1552
 unmap_vmas+0x241/0x370 mm/memory.c:1582
 exit_mmap+0x4d7/0x960 mm/mmap.c:3094
 __mmput+0x154/0x5f0 kernel/fork.c:994
 mmput+0xa7/0xe0 kernel/fork.c:1015
 exit_mm+0x6dd/0x790 kernel/exit.c:545
 do_exit+0xbf7/0x3890 kernel/exit.c:854
 do_group_exit+0x1a0/0x350 kernel/exit.c:970
 get_signal+0x1425/0x1ef0 kernel/signal.c:2468
 do_signal+0x120/0x2090 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
 syscall_return_slowpath+0xdb/0x700 arch/x86/entry/common.c:268
 do_syscall_64+0x1ab/0x220 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x45df89
Code: Bad RIP value.
RSP: 002b:000000c420065850 EFLAGS: 00000246 ORIG_RAX: 00000000000000e8
RAX: fffffffffffffffc RBX: 00000000ffffffff RCX: 000000000045df89
RDX: 0000000000000080 RSI: 000000c420065890 RDI: 0000000000000004
RBP: 000000c420065e90 R08: 0000000000000003 R09: 000000c42007ef00
R10: 00000000ffffffff R11: 0000000000000246 R12: 000000c428a9fa78
R13: 000000000000000f R14: 0000000000b74100 R15: 0000000000000cf3
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
CR2: 0000000000000050
---[ end trace d5a9f7c8983ae185 ]---
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:ffff8801a662ee00 EFLAGS: 00010006
RAX: ffffea00034bea48 RBX: ffffea00034bc000 RCX: 0000000000000071
RDX: 0000000000000000 RSI: 0000000000000009 RDI: ffffea0003984000
RBP: ffff8801a662ee48 R08: 0000000000480020 R09: 0000000000000002
R10: 0000000000000000 R11: ffffffff81c1cc50 R12: 0000000000000200
R13: ffff8801c672d880 R14: 0000000000000009 R15: ffffea0003aa4000
FS:  000000c420028e68(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000045df5f CR3: 0000000009830000 CR4: 00000000001406e0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600