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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc5c83b7f5f8 Linux 6.1.178
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10302449580000
kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=b402235664a10e0b8b02
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/96393e4697a3/disk-dc5c83b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0d4afce44fab/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4787e310d875/Image-dc5c83b7.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b40223...@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
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: 1 PID: 16133 Comm: syz.0.3765 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : dummy_udc_start+0xdc/0x1dc drivers/usb/gadget/udc/dummy_hcd.c:1003
lr : dummy_udc_start+0xb0/0x1dc drivers/usb/gadget/udc/dummy_hcd.c:1005
sp : ffff800021467660
x29: ffff800021467660 x28: 1fffe0001a407e01 x27: 1fffe0001a407e00
x26: 1fffe0001887c826 x25: dfff800000000000 x24: 1fffe0001a407e96
x23: ffff80000dcebb10 x22: dfff800000000000 x21: 0000000000000002
x20: 0000000000000000 x19: ffff0000c43e4050 x18: 0000000000000000
x17: 0000000000000000 x16: ffff800011b90540 x15: 0000000000000002
x14: 0000000000000005 x13: 0000000000ff0100 x12: 0000000000080000
x11: 00000000000094cf x10: ffff800022049000 x9 : ffff80000dcebbc0
x8 : 0000000000000000 x7 : ffff80000dce592c x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff8000082d44b0
x2 : ffff0000f3958000 x1 : ffff800016f205c0 x0 : 0000000000000002
Call trace:
dummy_udc_start+0xdc/0x1dc drivers/usb/gadget/udc/dummy_hcd.c:1003
usb_gadget_udc_start_locked drivers/usb/gadget/udc/core.c:1227 [inline]
gadget_bind_driver+0x31c/0x684 drivers/usb/gadget/udc/core.c:1656
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x3a0/0xac4 drivers/base/dd.c:638
__driver_probe_device+0x1c8/0x368 drivers/base/dd.c:804
driver_probe_device+0x78/0x324 drivers/base/dd.c:834
__driver_attach+0x3bc/0x614 drivers/base/dd.c:1220
bus_for_each_dev+0x148/0x1d0 drivers/base/bus.c:303
driver_attach+0x50/0x60 drivers/base/dd.c:1237
bus_add_driver+0x2c0/0x518 drivers/base/bus.c:620
driver_register+0x200/0x37c drivers/base/driver.c:246
usb_gadget_register_driver_owner+0xf0/0x25c drivers/usb/gadget/udc/core.c:1730
raw_ioctl_run drivers/usb/gadget/legacy/raw_gadget.c:549 [inline]
raw_ioctl+0x1014/0x326c drivers/usb/gadget/legacy/raw_gadget.c:1262
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
__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: 969f1d21 14000002 969f1d1f d343fe88 (38766908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 969f1d21 bl 0xfffffffffa7c7484
4: 14000002 b 0xc
8: 969f1d1f bl 0xfffffffffa7c7484
c: d343fe88 lsr x8, x20, #3
* 10: 38766908 ldrb w8, [x8, x22] <-- trapping instruction


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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: dc5c83b7f5f8 Linux 6.1.178
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=1296d88e580000

kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=b402235664a10e0b8b02
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=148e2232580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1614b2ea580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/96393e4697a3/disk-dc5c83b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0d4afce44fab/vmlinux-dc5c83b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4787e310d875/Image-dc5c83b7.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b40223...@syzkaller.appspotmail.com

dummy_hcd dummy_hcd.0: remove, state 4
usb usb1: USB disconnect, device number 1
dummy_hcd dummy_hcd.0: stopped
dummy_hcd dummy_hcd.0: USB bus 1 deregistered

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: 4463 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : dummy_udc_start+0xdc/0x1dc drivers/usb/gadget/udc/dummy_hcd.c:1003

lr : dummy_udc_start+0xd8/0x1dc drivers/usb/gadget/udc/dummy_hcd.c:1005
sp : ffff800020ff7660
x29: ffff800020ff7660 x28: 1fffe0001a3c1e01 x27: 1fffe0001a3c1e00
x26: 1fffe0001a666026 x25: dfff800000000000 x24: 1fffe0001a3c1e96
x23: ffff80000dcebb10 x22: dfff800000000000 x21: 0000000000000003
x20: 0000000000000000 x19: ffff0000d3330050 x18: 0000000000000000
x17: ffff80000de775d8 x16: ffff800011b90540 x15: 0000000000000000
x14: 0000000000000005 x13: 0000000000ff0100 x12: ffff800016f205f0
x11: ff0080000dcebbe8 x10: 0000000000000000 x9 : ffff80000dcebbe8
x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff8000082d44b0
x2 : ffff0000e0919c00 x1 : ffff800016f205c0 x0 : 0000000000000003

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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