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

[Greg KH <gregkh@linuxfoundation.org>]

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@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=8753715f05759f1a10de
> Tested-by: syzbot+8753715f05759f1a10de@syzkaller.appspotmail.com
> Link: https://lore.kernel.org/all/20260815143427.19066-1-kartikey406@gmail.com/T/ [v1]
> Link: https://lore.kernel.org/all/20260816015051.13184-1-kartikey406@gmail.com/T/ [v2]
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
> ---

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