Re: [PATCH v3] usbip: vhci_hcd: let the driver core manage the sysfs attributes

[Deepanshu Kartikey]

On Mon, Aug 31, 2026 at 3:36 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Sun, Aug 16, 2026 at 11:40:34AM +0530, Deepanshu Kartikey wrote:
> > The vhci attribute group is created in vhci_start() and removed in
> > vhci_stop(), guarded by usb_hcd_is_primary_hcd(). Both run from
> > usb_add_hcd()/usb_remove_hcd(), which are called once per hcd, so the
> > attach attribute is live while only one of the two hcds exists: it is
> > created during the first usb_add_hcd() before vhci_hcd_ss is set, and it
> > survives the first usb_put_hcd() on removal. A concurrent write to attach
> > can therefore reach a NULL or freed vhci_hcd_ss.
> >
> > Register the group as dev_groups on the platform driver instead, so the
> > driver core creates the files before probe and removes them after remove
> > returns, and drop the sysfs_create_group()/sysfs_remove_group() calls from
> > the driver. The attributes have always been created only on vhci_hcd.0;
> > an is_visible() callback keeps them there.
> >
> > vhci_init_attr_group() is moved into vhci_hcd_init() ahead of
> > platform_driver_register() so the group is populated before the core
> > reads it. The attribute array is still built at runtime because the
> > number of status attributes comes from CONFIG_USBIP_VHCI_NR_HCS and the
> > preprocessor cannot emit a variable number of __ATTR() declarations.
> >
> > Fixes: 1c9de5bf4286 ("usbip: vhci-hcd: Add USB3 SuperSpeed support")
> > Reported-by: syzbot+8753715f05759f1a10de@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=8753715f05759f1a10de
> > Tested-by: syzbot+8753715f05759f1a10de@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Link: https://lore.kernel.org/all/20260815143427.19066-1-kartikey406@xxxxxxxxx/T/ [v1]
> > Link: https://lore.kernel.org/all/20260816015051.13184-1-kartikey406@xxxxxxxxx/T/ [v2]
> > Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>
> > ---
>
> Did you forget an Assisted-by: tag?
>

Thanks for reminding me. I will add it and send patch v4.

Deepanshu