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Subject[syzbot] BUG: unable to handle kernel NULL pointer dereference in device_find_child
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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=17a90b58880000
kernel config: https://syzkaller.appspot.com/x/.config?x=3a4a45d2d827c1e
dashboard link: https://syzkaller.appspot.com/bug?extid=6a462bc8fbe652f7d3fd
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=166df61c880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=160c288a880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e8e91bc79312/disk-bbed346d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c1cb3fb3b77e/vmlinux-bbed346d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6a462bc8fbe652f7d3fd@syzkaller.appspotmail.com

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058
Mem abort info:
ESR = 0x0000000096000006
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 = 0x00000006
CM = 0, WnR = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=000000010b53c000
[0000000000000058] pgd=080000010b5e4003, p4d=080000010b5e4003, pud=0800000109b02003, pmd=0000000000000000
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 3038 Comm: syz-executor292 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 : ffff80001282ba10
x29: ffff80001282ba10 x28: ffff0000c10a3500 x27: 0001000000000000
x26: 0000000000000000 x25: 0000000000000000 x24: ffff0000c3f47000
x23: ffff80000d832b20 x22: ffff0000ca8a0000 x21: ffff0000c3f43538
x20: 0000000000000000 x19: ffff80001282ba68 x18: 00000000000000c0
x17: ffff80000dd0b198 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000002 x12: ffff80000d833180
x11: ff808000096ae804 x10: 0000000000000000 x9 : ffff8000096ae804
x8 : ffff0000c10a3500 x7 : ffff8000095d2cfc x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff80000b97020c x1 : ffff80001282ba68 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_rfkill_set_block+0x98/0x198 net/bluetooth/hci_core.c:947
rfkill_set_block+0xb4/0x1f8 net/rfkill/core.c:345
rfkill_fop_write+0x358/0x3f8 net/rfkill/core.c:1286
vfs_write+0x1a4/0x46c fs/read_write.c:576
ksys_write+0xb4/0x160 fs/read_write.c:631
__do_sys_write fs/read_write.c:643 [inline]
__se_sys_write fs/read_write.c:640 [inline]
__arm64_sys_write+0x24/0x34 fs/read_write.c:640
__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


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
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syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

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