BUG: unable to handle kernel NULL pointer dereference in exit_task_stack_account

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 65762d97e6fa Merge branch 'for-next/perf' 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=15125fe5880000
kernel config: https://syzkaller.appspot.com/x/.config?x=56d0c7c3a2304e8f
dashboard link: https://syzkaller.appspot.com/bug?extid=1d1c93741a8fb14abca8
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
CC: [ak...@linux-foundation.org big...@linutronix.de b...@vger.kernel.org bra...@kernel.org ebie...@xmission.com linux-...@vger.kernel.org lu...@kernel.org tg...@linutronix.de]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/52f702197b30/disk-65762d97.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/72189c2789ce/vmlinux-65762d97.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ec0349196c98/Image-65762d97.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1d1c93...@syzkaller.appspotmail.com

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
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=0000000151b74000
[0000000000000000] pgd=080000014d125003, p4d=080000014d125003, pud=0000000000000000
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 16876 Comm: syz-executor.1 Not tainted 6.1.0-rc6-syzkaller-32653-g65762d97e6fa #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 : account_kernel_stack kernel/fork.c:495 [inline]
pc : exit_task_stack_account+0x2c/0x39c kernel/fork.c:508
lr : exit_task_stack_account+0x20/0x39c kernel/fork.c:507
sp : ffff80002249bc10
x29: ffff80002249bc10 x28: ffff0000c58acec0 x27: 0000000000000001
x26: ffff0000c58ad450 x25: ffff0000c58ad450 x24: ffff000108e99a40
x23: ffff80002249bc60 x22: ffff00010f8fb780 x21: ffff0000c58acec0
x20: 0000000000000000 x19: ffff0000c58acec0 x18: 00000000000000fe
x17: ffff80000c0cd83c x16: ffff80000dbe6158 x15: ffff0000c58acec0
x14: 0000000000000010 x13: 00000000ffffffff x12: ffff0000c58acec0
x11: ff808000080f0d8c x10: 0000000000000000 x9 : ffff8000080f0d8c
x8 : 0000000000000000 x7 : ffff8000085134c8 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 000000000000039c x1 : 0000000043736564 x0 : 0000000000000000
Call trace:
account_kernel_stack kernel/fork.c:495 [inline]
exit_task_stack_account+0x2c/0x39c kernel/fork.c:508
do_exit+0x924/0xcac kernel/exit.c:862
do_group_exit+0x98/0xcc kernel/exit.c:950
get_signal+0xabc/0xb2c kernel/signal.c:2858
do_signal+0x128/0x438 arch/arm64/kernel/signal.c:1071
do_notify_resume+0xc0/0x1f0 arch/arm64/kernel/signal.c:1124
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
asm_exit_to_user_mode+0x70/0x84 arch/arm64/kernel/entry-common.c:149
ret_from_fork+0x1c/0x20 arch/arm64/kernel/entry.S:866
Code: 9406d2f4 f94ace76 2a1f03e0 f94012c8 (f9400114)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 9406d2f4 bl 0x1b4bd0
4: f94ace76 ldr x22, [x19, #5528]
8: 2a1f03e0 mov w0, wzr
c: f94012c8 ldr x8, [x22, #32]
* 10: f9400114 ldr x20, [x8] <-- trapping instruction


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.