[syzbot] [net?] BUG: unable to handle kernel paging request in ndisc_alloc_skb

[syzbot] [net?] BUG: unable to handle kernel paging request in ndisc_alloc_skb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    7a19f0cc94ad 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=16df313e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=26d6221a572842ac
dashboard link: https://syzkaller.appspot.com/bug?extid=7b5c2544e5ff37a729cb
compiler:       Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1555fda9580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/296cd4b77dbf/disk-7a19f0cc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e57669ed895f/vmlinux-7a19f0cc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c679c1ad76d4/Image-7a19f0cc.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7b5c2544e5ff37a729cb@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff80000000020c
KASAN: probably user-memory-access in range [0x0000000000001060-0x0000000000001067]
Mem abort info:
  ESR = 0x0000000096000005
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x05: level 1 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
  CM = 0, WnR = 0, TnD = 0, TagAccess = 0
  GCS = 0, Overlay = 0, DirtyBit = 0
[dfff80000000020c] address between user and kernel address ranges
Internal error: Oops: 0000000096000005 [#1]  SMP
Modules linked in:
CPU: 0 UID: 0 PID: 12 Comm: kworker/u8:0 Tainted: G   M                syzkaller #0 PREEMPT 
Tainted: [M]=MACHINE_CHECK
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/23/2026
Workqueue: ipv6_addrconf addrconf_dad_work
pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
pc : ndisc_alloc_skb+0x284/0x460 net/ipv6/ndisc.c:435
lr : read_pnet_rcu include/net/net_namespace.h:431 [inline]
lr : dev_net_rcu include/linux/netdevice.h:2816 [inline]
lr : ndisc_alloc_skb+0x270/0x460 net/ipv6/ndisc.c:435
sp : ffff80008f9178c0
x29: ffff80008f9178c0 x28: 1fffe00019eaa40d x27: 0000000000000001
x26: ffff80008f917900 x25: 1ffff00011f22f20 x24: ffff0000d5973990
x23: ffff0000d5973976 x22: dfff800000000000 x21: 0000000000000000
x20: 0000000000001060 x19: ffff0000d59738c0 x18: 00000000d557e235
x17: 0000000006512135 x16: dfff800000000000 x15: 0000000000000001
x14: 00000000001cb30b x13: 0000000000000009 x12: 0000000000000009
x11: 00000000f2fb2cc2 x10: 0000000000000003 x9 : 0000000000000000
x8 : 000000000000020c x7 : ffff80008579a0c0 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff80008579a1a4
x2 : 0000000000000001 x1 : ffff0000c1a00000 x0 : 0000000000000000
Call trace:
 ndisc_alloc_skb+0x284/0x460 net/ipv6/ndisc.c:435 (P)
 ndisc_ns_create+0x1f4/0x54c net/ipv6/ndisc.c:627
 ndisc_send_ns+0xbc/0x168 net/ipv6/ndisc.c:669
 addrconf_dad_work+0x77c/0xfe8 net/ipv6/addrconf.c:4318
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0x91c/0x1250 kernel/workqueue.c:3479
 worker_thread+0x798/0xbd0 kernel/workqueue.c:3560
 kthread+0x304/0x3d4 kernel/kthread.c:436
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854
Code: 96ba87a4 52820c08 8b0802b4 d343fe88 (38766908) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	96ba87a4 	bl	0xfffffffffaea1e90
   4:	52820c08 	mov	w8, #0x1060                	// #4192
   8:	8b0802b4 	add	x20, x21, x8
   c:	d343fe88 	lsr	x8, x20, #3
* 10:	38766908 	ldrb	w8, [x8, x22] <-- trapping instruction


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