Re: [PATCH v2] usb: usbtest: disable dynamic ID support

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Aug 06, 2026 at 02:25:11PM +0000, Aleksandr Nogikh wrote:
> The usbtest driver relies on the driver_info field of struct usb_device_id
> to point to a valid struct usbtest_info descriptor. This structure contains
> essential test configurations, such as endpoint addresses and test modes,
> which are required during probe.
> 
> When a user dynamically adds a new device ID via the sysfs new_id
> interface without specifying a reference device, the USB core initializes
> driver_info to 0 (NULL). When a matching device is subsequently probed,
> usbtest_probe() unconditionally casts driver_info to a struct usbtest_info
> pointer and dereferences it, leading to a NULL pointer dereference crash:
> 
>   Oops: general protection fault, probably for non-canonical address
>   0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI
>   KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
>   RIP: 0010:usbtest_probe+0x3b9/0x1280 drivers/usb/misc/usbtest.c:2822
> 
> Because usbtest strictly requires pre-defined usbtest_info descriptors
> to function, dynamic ID binding via sysfs is fundamentally unsupported
> for this driver.
> 
> Fix this by setting .no_dynamic_id = 1 on usbtest_driver. This instructs
> the USB core to skip creating the new_id and remove_id sysfs interfaces
> for usbtest, preventing invalid dynamic ID entries from being created.
> 
> Reported-by: syzbot+7e1e5911f9eac50bedc7@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=7e1e5911f9eac50bedc7
> Signed-off-by: Aleksandr Nogikh <nogikh@google.com>

Shouldn't this also get a cc: stable?

thanks,

greg k-h