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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    bbed346d5a96 Merge branch 'for-next/core' into for-kernelci
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=13d5fa0a880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=aae2d21e7dd80684
dashboard link: https://syzkaller.appspot.com/bug?extid=dd585485bb7caaa89f57
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=1006b058880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=100b0484880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/11078f50b80b/disk-bbed346d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/398e5f1e6c84/vmlinux-bbed346d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dd585485bb7caaa89f57@xxxxxxxxxxxxxxxxxxxxxxxxx

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058
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
user pgtable: 4k pages, 48-bit VAs, pgdp=0000000107dda000
[0000000000000058] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 3030 Comm: syz-executor336 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 : klist_next+0x28/0x18c lib/klist.c:377
lr : klist_next+0x24/0x18c lib/klist.c:376
sp : ffff8000126fba20
x29: ffff8000126fba20 x28: 00000000000e0003 x27: 0000000000002000
x26: 0000000000000000 x25: 0000000000000000 x24: ffff0000c657b000
x23: ffff80000d832b20 x22: ffff0000ca924000 x21: ffff0000c6578538
x20: 0000000000000000 x19: ffff8000126fba78 x18: 00000000000000c0
x17: ffff80000dd0b198 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000002 x12: ffff80000d833180
x11: ff808000096ae804 x10: 0000000000000000 x9 : ffff8000096ae804
x8 : ffff0000c62c0000 x7 : ffff8000095d2cfc x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff80000b97020c x1 : ffff8000126fba78 x0 : 0000000000000000
Call trace:
 klist_next+0x28/0x18c lib/klist.c:377
 next_device drivers/base/core.c:3756 [inline]
 device_find_child+0x50/0x114 drivers/base/core.c:3899
 hci_conn_del_sysfs+0x54/0xfc net/bluetooth/hci_sysfs.c:71
 hci_conn_cleanup+0x2d4/0x380 net/bluetooth/hci_conn.c:147
 hci_conn_del+0x144/0x2a8 net/bluetooth/hci_conn.c:1022
 hci_conn_hash_flush+0xe8/0x148 net/bluetooth/hci_conn.c:2367
 hci_dev_close_sync+0x48c/0x9e0 net/bluetooth/hci_sync.c:4476
 hci_dev_do_close net/bluetooth/hci_core.c:554 [inline]
 hci_unregister_dev+0xe4/0x280 net/bluetooth/hci_core.c:2682
 vhci_release+0x44/0x80 drivers/bluetooth/hci_vhci.c:568
 __fput+0x198/0x3dc fs/file_table.c:320
 ____fput+0x20/0x30 fs/file_table.c:353
 task_work_run+0xc4/0x14c kernel/task_work.c:177
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x26c/0xbe0 kernel/exit.c:795
 do_group_exit+0x60/0xe8 kernel/exit.c:925
 __do_sys_exit_group kernel/exit.c:936 [inline]
 __se_sys_exit_group kernel/exit.c:934 [inline]
 __wake_up_parent+0x0/0x40 kernel/exit.c:934
 __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 arch/arm64/kernel/entry.S:581
Code: 910003fd aa0003f3 97afc505 a9405260 (f9402c18) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	910003fd 	mov	x29, sp
   4:	aa0003f3 	mov	x19, x0
   8:	97afc505 	bl	0xfffffffffebf141c
   c:	a9405260 	ldp	x0, x20, [x19]
* 10:	f9402c18 	ldr	x24, [x0, #88] <-- trapping instruction


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