BUG: unable to handle kernel paging request in nilfs_mdt_fetch

Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported
KASAN: use-after-free Read in nilfs_segctor_confirm nilfs	C	inconclusive		19	793d	812d

Title	Replies (including bot)	Last reply
[syzbot] BUG: unable to handle kernel paging request in nilfs_mdt_fetch_dirty	1 (2)	2022/11/08 01:59

Unable to handle kernel paging request at virtual address fffffffffffffeb8
Mem abort info:
  ESR = 0x0000000096000004
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000004
  CM = 0, WnR = 0
swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000001c566b000
[fffffffffffffeb8] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 7614 Comm: segctord Not tainted 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : nilfs_mdt_fetch_dirty+0x1c/0x94 fs/nilfs2/mdt.c:394
lr : nilfs_mdt_fetch_dirty+0x18/0x94 fs/nilfs2/mdt.c:391
sp : ffff80001f553cc0
x29: ffff80001f553cc0 x28: 0000000000000000 x27: 0000000000000000
x26: 0000000000000001 x25: ffff00011b0cc800 x24: ffff00011b0cc800
x23: 0000000000000001 x22: 0000000000000001 x21: ffff00011b0cc800
x20: ffff00011b198900 x19: 0000000000000000 x18: 0000000000000107
x17: ffff80000bffd6bc x16: ffff80000db49158 x15: ffff00012640cf80
x14: 0000000000000008 x13: 00000000ffffffff x12: ffff00012640cf80
x11: ff80800008f55b48 x10: 0000000000000000 x9 : ffff800008f55b48
x8 : fffffffffffffeb8 x7 : ffff8000082160c0 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000006 x1 : ffff00011b198900 x0 : 0000000000000000
Call trace:
 nilfs_mdt_fetch_dirty+0x1c/0x94 fs/nilfs2/mdt.c:394
 nilfs_test_metadata_dirty+0x2c/0x148 fs/nilfs2/segment.c:813
 nilfs_segctor_confirm+0x30/0x1a8 fs/nilfs2/segment.c:837
 nilfs_segctor_construct+0x78/0x380 fs/nilfs2/segment.c:2374
 nilfs_segctor_thread_construct fs/nilfs2/segment.c:2483 [inline]
 nilfs_segctor_thread+0x180/0x660 fs/nilfs2/segment.c:2566
 kthread+0x12c/0x158 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
Code: 910003fd aa0003f3 97cd2834 d1052268 (f9400100) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	910003fd 	mov	x29, sp
   4:	aa0003f3 	mov	x19, x0
   8:	97cd2834 	bl	0xffffffffff34a0d8
   c:	d1052268 	sub	x8, x19, #0x148
* 10:	f9400100 	ldr	x0, [x8] <-- trapping instruction