[v6.1] BUG: unable to handle kernel paging request in dummy_udc_stop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e4f7d8be268e Linux 6.1.182
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1346d6c6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=b88711b6911b85ab5788
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7cd9b1875376/disk-e4f7d8be.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4b5d35d18c31/vmlinux-e4f7d8be.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d5ee64c2af77/Image-e4f7d8be.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b88711...@syzkaller.appspotmail.com

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
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: 5072 Comm: syz.3.218 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : dummy_udc_stop+0x94/0x2f4 drivers/usb/gadget/udc/dummy_hcd.c:1034
lr : gadget_to_dummy_hcd drivers/usb/gadget/udc/dummy_hcd.c:316 [inline]
lr : dummy_udc_stop+0x64/0x2f4 drivers/usb/gadget/udc/dummy_hcd.c:1033
x26: 1fffe0001a3abe00 x25: dfff800000000000 x24: 1fffe0001a3abe96
x23: dfff800000000000 x22: ffff800013110b18 x21: ffff0000d0fbcc00
x20: 0000000000000003 x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000000000 x16: ffff800011b90080 x15: 0000000000000000
x14: 0000000000000001 x13: 1ffff00004dd4ed0 x12: 0000000000080000
x11: ff0080000dceb890 x10: 0000000000000002 x9 : 0000000000000658
x8 : 0000000000000000 x7 : ffff80000dce59ec x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff8000082d44b4
x2 : ffff0000cb37b800 x1 : 0000000000000003 x0 : 0000000000000005
Call trace:
dummy_udc_stop+0x94/0x2f4 drivers/usb/gadget/udc/dummy_hcd.c:1034
usb_gadget_udc_stop_locked drivers/usb/gadget/udc/core.c:1255 [inline]
gadget_unbind_driver+0x204/0x35c drivers/usb/gadget/udc/core.c:1705
device_remove drivers/base/dd.c:547 [inline]
__device_release_driver drivers/base/dd.c:1279 [inline]
device_release_driver_internal+0x3d4/0x6e4 drivers/base/dd.c:1305
driver_detach+0x1e8/0x2ac drivers/base/dd.c:1368
bus_remove_driver+0x120/0x240 drivers/base/bus.c:679
driver_unregister+0x78/0xac drivers/base/driver.c:274
usb_gadget_unregister_driver+0x50/0x78 drivers/usb/gadget/udc/core.c:1762
unregister_gadget drivers/usb/gadget/configfs.c:253 [inline]
gadget_dev_desc_UDC_store+0x124/0x268 drivers/usb/gadget/configfs.c:280
flush_write_buffer fs/configfs/file.c:207 [inline]
configfs_write_iter+0x260/0x338 fs/configfs/file.c:229
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x3c8/0x7c8 fs/read_write.c:584
ksys_write+0x12c/0x228 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 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: aa1303e0 96b0241f f9400273 d343fe68 (38776908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: aa1303e0 mov x0, x19
4: 96b0241f bl 0xfffffffffac09080
8: f9400273 ldr x19, [x19]
c: d343fe68 lsr x8, x19, #3
* 10: 38776908 ldrb w8, [x8, x23] <-- trapping instruction


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