Subject: Re: [syzbot] BUG: unable to handle kernel paging request in p9_client_disconnect

From: syzbot <[email-masked]>
Date: Thu, 05 Jan 2023 21:38:48 -0800

syzbot has found a reproducer for the following issue on:

HEAD commit:    247f34f7b803 Linux 6.1-rc2
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=145dcb52480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa9bed8d6a8992a0
dashboard link: https://syzkaller.appspot.com/bug?extid=ea8b28e8dca42fc3bcbe
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=1360a90c480000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1580e9e6480000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/05f9a7fca332/disk-247f34f7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ec50c3ad7d48/vmlinux-247f34f7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1446f94b11ed/Image-247f34f7.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

Unable to handle kernel paging request at virtual address 0032503900080052
Mem abort info:
  ESR = 0x0000000096000044
  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 = 0x00000044
  CM = 0, WnR = 1
[0032503900080052] address between user and kernel address ranges
Internal error: Oops: 0000000096000044 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 3076 Comm: syz-executor424 Not tainted 6.1.0-rc2-syzkaller-154433-g247f34f7b803 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : p9_client_disconnect+0x1c/0x30 net/9p/client.c:1067
lr : p9_client_disconnect+0x18/0x30 net/9p/client.c:1065
sp : ffff800012e43ca0
x29: ffff800012e43ca0 x28: ffff0000cb48cec0 x27: 0000000000000000
x26: 00000000000000c0 x25: 0000000000000002 x24: ffff80000d37d050
x23: ffff80000d379000 x22: 0000000000000000 x21: 0000000000000000
x20: ffff0000cc82cf00 x19: 3032503900080002 x18: 0000000000000035
x17: 4553006964623d4d x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: ffff0000c5860c18 x12: ffff0000ccb854d8
x11: ff8080000be7a520 x10: 0000000000000000 x9 : ffff80000be7a520
x8 : 0000000000000002 x7 : 0000000000000000 x6 : ffff80000c0374d8
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff0000cb48cec0 x1 : 0000000000000000 x0 : 3032503900080002
Call trace:
 p9_client_disconnect+0x1c/0x30
 v9fs_session_cancel+0x20/0x30 fs/9p/v9fs.c:530
 v9fs_kill_super+0x2c/0x50 fs/9p/vfs_super.c:225
 deactivate_locked_super+0x70/0xe8 fs/super.c:331
 deactivate_super+0xd0/0xd4 fs/super.c:362
 cleanup_mnt+0x184/0x1c0 fs/namespace.c:1186
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1193
 task_work_run+0x100/0x148 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 do_notify_resume+0x174/0x1f0 arch/arm64/kernel/signal.c:1127
 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]
 el0_svc+0x9c/0x150 arch/arm64/kernel/entry-common.c:637
 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 9710b2fd 52800048 (b9005268) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	910003fd 	mov	x29, sp
   4:	aa0003f3 	mov	x19, x0
   8:	9710b2fd 	bl	0xfffffffffc42cbfc
   c:	52800048 	mov	w8, #0x2                   	// #2
* 10:	b9005268 	str	w8, [x19, #80] <-- trapping instruction