linux-kernel - [syzbot] [rcu?] BUG: unable to handle kernel paging request in rcu_cblist

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Message-ID: <68b066dd.a70a0220.f8cc2.007b.GAE@google.com>
Date: Thu, 28 Aug 2025 07:25:33 -0700
From: syzbot <syzbot+dfae5535e0da40eb9879@...kaller.appspotmail.com>
To: boqun.feng@...il.com, frederic@...nel.org, jiangshanlai@...il.com, 
	joelagnelf@...dia.com, josh@...htriplett.org, linux-kernel@...r.kernel.org, 
	mathieu.desnoyers@...icios.com, neeraj.upadhyay@...nel.org, 
	paulmck@...nel.org, qiang.zhang@...ux.dev, rcu@...r.kernel.org, 
	rostedt@...dmis.org, syzkaller-bugs@...glegroups.com, urezki@...il.com
Subject: [syzbot] [rcu?] BUG: unable to handle kernel paging request in rcu_cblist_dequeue

Hello,

syzbot found the following issue on:

HEAD commit:    8f5ae30d69d7 Linux 6.17-rc1
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=1617e634580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8c5ac3d8b8abfcb
dashboard link: https://syzkaller.appspot.com/bug?extid=dfae5535e0da40eb9879
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/18a2e4bd0c4a/disk-8f5ae30d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b5395881b25/vmlinux-8f5ae30d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e875f4e3b7ff/Image-8f5ae30d.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dfae5535e0da40eb9879@...kaller.appspotmail.com

Unable to handle kernel paging request at virtual address ffff3ff7ee0a2600
KASAN: maybe wild-memory-access in range [0xfffdffbf70513000-0xfffdffbf70513007]
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, ISS2 = 0x00000000
  CM = 0, WnR = 0, TnD = 0, TagAccess = 0
  GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000206ec9000
[ffff3ff7ee0a2600] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1]  SMP
Modules linked in:
CPU: 0 UID: 0 PID: 1816 Comm: kworker/0:2 Not tainted 6.17.0-rc1-syzkaller-g8f5ae30d69d7 #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Workqueue: rcu_gp srcu_invoke_callbacks
pstate: 03400005 (nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : rcu_cblist_dequeue+0x68/0xc8 kernel/rcu/rcu_segcblist.c:75
lr : srcu_invoke_callbacks+0x198/0x394 kernel/rcu/srcutree.c:1802
sp : ffff80009f9c7960
x29: ffff80009f9c7960 x28: ffff80009f9c79c0 x27: dfff800000000000
x26: ffff0000c5a5a918 x25: ffff0000c1092800 x24: fffffdffbf6e0e40
x23: 1ffff00013f38f3c x22: dfff800000000000 x21: ffff80009f9c79f0
x20: fffdffbf70513000 x19: ffff80009f9c79e0 x18: 0000000000000000
x17: ffff80010c5d9000 x16: ffff8000805293e8 x15: 0000000000000001
x14: 1fffffbff7edc1c8 x13: 0000000000000000 x12: 0000000000000000
x11: ffff800093306be8 x10: 0000000000000001 x9 : 1fffbff7ee0a2600
x8 : 0000000000000000 x7 : ffff8000805b4130 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000001 x3 : 0000000000000010
x2 : 0000000000000006 x1 : ffff80008edc258c x0 : ffff80009f9c79e0
Call trace:
 rcu_cblist_dequeue+0x68/0xc8 kernel/rcu/rcu_segcblist.c:74 (P)
 srcu_invoke_callbacks+0x198/0x394 kernel/rcu/srcutree.c:1802
 process_one_work+0x7e8/0x155c kernel/workqueue.c:3236
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3400
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
Code: f94002a8 d343fe89 d1000508 f90002a8 (38766928) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	f94002a8 	ldr	x8, [x21]
   4:	d343fe89 	lsr	x9, x20, #3
   8:	d1000508 	sub	x8, x8, #0x1
   c:	f90002a8 	str	x8, [x21]
* 10:	38766928 	ldrb	w8, [x9, x22] <-- trapping instruction


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