==================================================================
BUG: KASAN: null-ptr-deref in traverse_mounts fs/namei.c:1431 [inline]
BUG: KASAN: null-ptr-deref in handle_mounts fs/namei.c:1543 [inline]
BUG: KASAN: null-ptr-deref in step_into+0xe8/0xb48 fs/namei.c:1836
Read of size 4 at addr 0000000000000018 by task syz-executor/4304

CPU: 1 PID: 4304 Comm: syz-executor Not tainted 6.1.135-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_report+0x40/0x68 mm/kasan/report.c:430
 kasan_report+0xa8/0x100 mm/kasan/report.c:531
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x260/0x2a0 mm/kasan/generic.c:189
 __kasan_check_read+0x2c/0x3c mm/kasan/shadow.c:31
 traverse_mounts fs/namei.c:1431 [inline]
 handle_mounts fs/namei.c:1543 [inline]
 step_into+0xe8/0xb48 fs/namei.c:1836
 walk_component+0x1c8/0x364 fs/namei.c:2004
 lookup_last fs/namei.c:2455 [inline]
 path_lookupat+0x13c/0x3d0 fs/namei.c:2479
 filename_lookup+0x190/0x42c fs/namei.c:2508
 user_path_at_empty+0x5c/0x84 fs/namei.c:2905
 user_path_at include/linux/namei.h:57 [inline]
 ksys_umount fs/namespace.c:1823 [inline]
 __do_sys_umount fs/namespace.c:1831 [inline]
 __se_sys_umount fs/namespace.c:1829 [inline]
 __arm64_sys_umount+0xf4/0x178 fs/namespace.c:1829
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
==================================================================
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000018
Mem abort info:
  ESR = 0x0000000096000005
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x05: level 1 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000005
  CM = 0, WnR = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=000000012dfab000
[0000000000000018] pgd=0800000134116003, p4d=0800000134116003, pud=0000000000000000
Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4304 Comm: syz-executor Tainted: G    B              6.1.135-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : traverse_mounts fs/namei.c:1431 [inline]
pc : handle_mounts fs/namei.c:1543 [inline]
pc : step_into+0xe8/0xb48 fs/namei.c:1836
lr : traverse_mounts fs/namei.c:1431 [inline]
lr : handle_mounts fs/namei.c:1543 [inline]
lr : step_into+0xe8/0xb48 fs/namei.c:1836
sp : ffff8000208578c0
x29: ffff800020857980 x28: 1ffff0000410af63 x27: 1ffff0000410af24
x26: dfff800000000000 x25: 0000000000000080 x24: ffff800020857af4
x23: 0000000000000018 x22: 0000000000000080 x21: ffff800020857b18
x20: 1ffff0000410af5c x19: ffff800020857ae0 x18: ffff800011a7bd00
x17: 1fffe000367c2f76 x16: ffff800008042940 x15: 0000000040000000
x14: 0000000000000002 x13: 0000000000ff0100 x12: 0000000000ff0100
x11: ff00800008190f14 x10: 0000000000000000 x9 : 0000000000000000
x8 : 0000000000000000 x7 : 0000000000000004 x6 : ffff8000082516e4
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff800008190ed8
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
 traverse_mounts fs/namei.c:1431 [inline]
 handle_mounts fs/namei.c:1543 [inline]
 step_into+0xe8/0xb48 fs/namei.c:1836
 walk_component+0x1c8/0x364 fs/namei.c:2004
 lookup_last fs/namei.c:2455 [inline]
 path_lookupat+0x13c/0x3d0 fs/namei.c:2479
 filename_lookup+0x190/0x42c fs/namei.c:2508
 user_path_at_empty+0x5c/0x84 fs/namei.c:2905
 user_path_at include/linux/namei.h:57 [inline]
 ksys_umount fs/namespace.c:1823 [inline]
 __do_sys_umount fs/namespace.c:1831 [inline]
 __se_sys_umount fs/namespace.c:1829 [inline]
 __arm64_sys_umount+0xf4/0x178 fs/namespace.c:1829
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: b94002b6 52800081 aa1703e0 97fc104c (88dffef7) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	b94002b6 	ldr	w22, [x21]
   4:	52800081 	mov	w1, #0x4                   	// #4
   8:	aa1703e0 	mov	x0, x23
   c:	97fc104c 	bl	0xfffffffffff0413c
* 10:	88dffef7 	ldar	w23, [x23] <-- trapping instruction