[v6.1] BUG: unable to handle kernel paging request in fq_codel_enqueue (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=133352ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=3ac39748891ee2433e44
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cf55a056d548/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af13139876bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/02c231cd5348/Image-7c87defb.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3ac397...@syzkaller.appspotmail.com

device syzkaller0 entered promiscuous mode
Unable to handle kernel paging request at virtual address dfff800000000000
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
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
[dfff800000000000] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 7358 Comm: syz.2.977 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : dequeue_head net/sched/sch_fq_codel.c:120 [inline]
pc : fq_codel_drop net/sched/sch_fq_codel.c:168 [inline]
pc : fq_codel_enqueue+0x870/0x10d8 net/sched/sch_fq_codel.c:230
lr : fq_codel_drop net/sched/sch_fq_codel.c:162 [inline]
lr : fq_codel_enqueue+0x7e4/0x10d8 net/sched/sch_fq_codel.c:230
sp : ffff800021bb7180
x29: ffff800021bb7280 x28: 0000000000000000 x27: 0000000000000000
x26: 0000000000000000 x25: 0000000000000001 x24: ffff000104f40000
x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000000001
x20: ffff0000da8c3ad0 x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000420050 x16: ffff8000082d92bc x15: 0000000000000002
x14: 0000000000000003 x13: 1ffff00002a44071 x12: 0000000000080000
x11: 000000000000131e x10: dfff800000000000 x9 : 1fffe000209e8000
x8 : 0000000000000000 x7 : ffff8000083c1bd4 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff0000da8c3b28 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
dequeue_head net/sched/sch_fq_codel.c:120 [inline]
fq_codel_drop net/sched/sch_fq_codel.c:168 [inline]
fq_codel_enqueue+0x870/0x10d8 net/sched/sch_fq_codel.c:230
qdisc_enqueue include/net/sch_generic.h:854 [inline]
netem_dequeue+0xa78/0x1080 net/sched/sch_netem.c:737
dequeue_skb net/sched/sch_generic.c:295 [inline]
qdisc_restart net/sched/sch_generic.c:400 [inline]
__qdisc_run+0x1cc/0x133c net/sched/sch_generic.c:418
__dev_xmit_skb net/core/dev.c:3995 [inline]
__dev_queue_xmit+0xc40/0x3118 net/core/dev.c:4337
dev_queue_xmit+0x24/0x34 include/linux/netdevice.h:3051
packet_snd net/packet/af_packet.c:3127 [inline]
packet_sendmsg+0x2f9c/0x3fd0 net/packet/af_packet.c:3158
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
__sys_sendto+0x324/0x440 net/socket.c:2152
__do_sys_sendto net/socket.c:2164 [inline]
__se_sys_sendto net/socket.c:2160 [inline]
__arm64_sys_sendto+0xd8/0xf8 net/socket.c:2160
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: d2d0000a f2fbffea f9400317 d343fee8 (386a6908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: d2d0000a mov x10, #0x800000000000 // #140737488355328
4: f2fbffea movk x10, #0xdfff, lsl #48
8: f9400317 ldr x23, [x24]
c: d343fee8 lsr x8, x23, #3
* 10: 386a6908 ldrb w8, [x8, x10] <-- trapping instruction


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