[syzbot] BUG: unable to handle kernel NULL pointer dereference in dtInsertEntry

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    c194837ebb57 Merge branch 'for-next/core', remote-tracking..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=1271d188880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=15a770deac0c935a
dashboard link: https://syzkaller.appspot.com/bug?extid=c853277dcbfa2182e9aa
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10d2d470880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14717b18880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8d8ae425e7fa/disk-c194837e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c540d501ebe7/vmlinux-c194837e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c853277dcbfa2182e9aa@xxxxxxxxxxxxxxxxxxxxxxxxx

loop0: detected capacity change from 0 to 65535
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
Mem abort info:
  ESR = 0x0000000096000046
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000046
  CM = 0, WnR = 1
user pgtable: 4k pages, 48-bit VAs, pgdp=000000010b4bb000
[0000000000000008] pgd=080000010b405003, p4d=080000010b405003, pud=0800000107ba1003, pmd=0000000000000000
Internal error: Oops: 0000000096000046 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 3064 Comm: syz-executor267 Not tainted 6.0.0-rc6-syzkaller-17742-gc194837ebb57 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : dtInsertEntry+0x470/0x660 fs/jfs/jfs_dtree.c:3708
lr : dtInsertEntry+0x468/0x660 fs/jfs/jfs_dtree.c:3708
sp : ffff80000ff7b820
x29: ffff80000ff7b8a0 x28: ffff0000ca10aed8 x27: ffff0000ca10aef8
x26: 0000000000000000 x25: 000000000000000d x24: 0000000000000001
x23: 0000000000000000 x22: 0000000000000073 x21: 0000000000000006
x20: ffff80000ff7b908 x19: 0000000000000079 x18: 00000000000000c0
x17: ffff80000dd0b198 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000008000 x12: ffff80000d5335c0
x11: ff80800008d4c768 x10: 0000000000000000 x9 : 0000000000000000
x8 : 00000000000000ff x7 : ffff800008d5cfac x6 : 0000000000000000
x5 : 0000000000000000 x4 : ffff80000ff7b900 x3 : ffff80000ff7b908
x2 : ffff80000ff7b9b0 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
 dtInsertEntry+0x470/0x660
 dtInsert+0x21c/0x378 fs/jfs/jfs_dtree.c:886
 jfs_create+0x390/0x488 fs/jfs/namei.c:137
 lookup_open fs/namei.c:3413 [inline]
 open_last_lookups fs/namei.c:3481 [inline]
 path_openat+0x804/0x11c4 fs/namei.c:3688
 do_filp_open+0xdc/0x1b8 fs/namei.c:3718
 do_sys_openat2+0xb8/0x22c fs/open.c:1311
 do_sys_open fs/open.c:1327 [inline]
 __do_sys_openat fs/open.c:1343 [inline]
 __se_sys_openat fs/open.c:1338 [inline]
 __arm64_sys_openat+0xb0/0xe0 fs/open.c:1338
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
 el0t_64_sync+0x18c/0x190
Code: 370800d3 97d54f56 f9400fe9 52801fe8 (39002128) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	370800d3 	tbnz	w19, #1, 0x18
   4:	97d54f56 	bl	0xffffffffff553d5c
   8:	f9400fe9 	ldr	x9, [sp, #24]
   c:	52801fe8 	mov	w8, #0xff                  	// #255
* 10:	39002128 	strb	w8, [x9, #8] <-- trapping instruction


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