BUG: kernel NULL pointer dereference, address: 0000000000000120
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 8000000107763067 P4D 8000000107763067 PUD 0 
Oops: Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 1 UID: 0 PID: 4006 Comm: syz.0.31 Not tainted 6.13.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
RIP: 0010:shmem_mapping+0xb/0x20 mm/shmem.c:281
Code: 6b e2 07 00 48 89 df 5b e9 62 e2 07 00 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 c7 c0 40 98 22 83 <48> 39 87 20 01 00 00 0f 94 c0 c3 cc cc cc cc 66 0f 1f 44 00 00 90
RSP: 0018:ffffc900032cf7d0 EFLAGS: 00010002
RAX: ffffffff83229840 RBX: ffffea0004930040 RCX: 017ff6000002001d
RDX: ffffea0004930008 RSI: 0000000000000601 RDI: 0000000000000000
RBP: ffffea0004930080 R08: ffffc900032cf772 R09: 0000000000000002
R10: ffffea0004930000 R11: 0000000000000000 R12: ffffea0004930048
R13: ffffea0004930000 R14: ffffea0004930000 R15: ffff888110025aa0
FS:  00007fba226336c0(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000120 CR3: 000000011657e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __split_unmapped_folio+0x7ea/0xf60 mm/huge_memory.c:3794
 __folio_split+0x580/0x730 mm/huge_memory.c:4078
 truncate_inode_partial_folio+0x18a/0x200 mm/truncate.c:224
 shmem_undo_range+0x32b/0x650 mm/shmem.c:1144
 shmem_truncate_range mm/shmem.c:1224 [inline]
 shmem_fallocate+0x2f2/0x570 mm/shmem.c:3674
 vfs_fallocate+0x1bd/0x200 fs/open.c:338
 madvise_remove mm/madvise.c:1034 [inline]
 madvise_vma_behavior mm/madvise.c:1269 [inline]
 madvise_walk_vmas mm/madvise.c:1511 [inline]
 madvise_do_behavior+0x6c2/0x1400 mm/madvise.c:1646
 do_madvise mm/madvise.c:1744 [inline]
 __do_sys_madvise mm/madvise.c:1752 [inline]
 __se_sys_madvise mm/madvise.c:1750 [inline]
 __x64_sys_madvise+0x71/0xa0 mm/madvise.c:1750
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x8d/0x170 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fba2178cde9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fba22633038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007fba219a5fa0 RCX: 00007fba2178cde9
RDX: 0000000000000009 RSI: 0000000000600003 RDI: 0000400000000000
RBP: 00007fba2180e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fba219a5fa0 R15: 00007ffc4a617788
 </TASK>
Modules linked in:
CR2: 0000000000000120
---[ end trace 0000000000000000 ]---
RIP: 0010:shmem_mapping+0xb/0x20 mm/shmem.c:281
Code: 6b e2 07 00 48 89 df 5b e9 62 e2 07 00 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 c7 c0 40 98 22 83 <48> 39 87 20 01 00 00 0f 94 c0 c3 cc cc cc cc 66 0f 1f 44 00 00 90
RSP: 0018:ffffc900032cf7d0 EFLAGS: 00010002
RAX: ffffffff83229840 RBX: ffffea0004930040 RCX: 017ff6000002001d
RDX: ffffea0004930008 RSI: 0000000000000601 RDI: 0000000000000000
RBP: ffffea0004930080 R08: ffffc900032cf772 R09: 0000000000000002
R10: ffffea0004930000 R11: 0000000000000000 R12: ffffea0004930048
R13: ffffea0004930000 R14: ffffea0004930000 R15: ffff888110025aa0
FS:  00007fba226336c0(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000120 CR3: 000000011657e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 4 bytes skipped:
   0:	48 89 df             	mov    %rbx,%rdi
   3:	5b                   	pop    %rbx
   4:	e9 62 e2 07 00       	jmp    0x7e26b
   9:	66 90                	xchg   %ax,%ax
   b:	90                   	nop
   c:	90                   	nop
   d:	90                   	nop
   e:	90                   	nop
   f:	90                   	nop
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	f3 0f 1e fa          	endbr64
  1f:	48 c7 c0 40 98 22 83 	mov    $0xffffffff83229840,%rax
* 26:	48 39 87 20 01 00 00 	cmp    %rax,0x120(%rdi) <-- trapping instruction
  2d:	0f 94 c0             	sete   %al
  30:	c3                   	ret
  31:	cc                   	int3
  32:	cc                   	int3
  33:	cc                   	int3
  34:	cc                   	int3
  35:	66 0f 1f 44 00 00    	nopw   0x0(%rax,%rax,1)
  3b:	90                   	nop