Re: [PATCH 2/2] usb: gadget: f_mass_storage: ignore class requests while inactive

[Alan Stern <stern@rowland.harvard.edu>]

On Mon, Sep 07, 2026 at 08:58:42AM +0000, Keisuke Tsukuda wrote:
> SET_CONFIGURATION is handled asynchronously by the mass-storage thread.
> A class request can arrive after the composite core selects the function
> but before the thread installs common->fsg, or while the function is being
> disabled.
> 
> fsg_setup() already rejects this state with -EOPNOTSUPP, but checking it
> through fsg_is_set() also emits a warning. Check the active function
> directly so normal requests during a configuration transition are rejected
> without hiding fsg_is_set() warnings from other internal paths.
> 
> Fixes: 8876f5e7d3b2 ("USB: gadget: f_mass_storage: added eject callback")
> Reported-by: syzbot+d31109047baed8f3b590@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=d31109047baed8f3b590
> Signed-off-by: Keisuke Tsukuda <tkdkei@outlook.jp>
> ---
>  drivers/usb/gadget/function/f_mass_storage.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
> index a50743c..52d486a 100644
> --- a/drivers/usb/gadget/function/f_mass_storage.c
> +++ b/drivers/usb/gadget/function/f_mass_storage.c
> @@ -463,7 +463,7 @@ static int fsg_setup(struct usb_function *f,
>  	u16			w_value = le16_to_cpu(ctrl->wValue);
>  	u16			w_length = le16_to_cpu(ctrl->wLength);
>  
> -	if (!fsg_is_set(fsg->common))
> +	if (!fsg->common->fsg)

I'd feel better about this if there was a comment here explaining why 
calling fsg_is_set() is a bad idea.

Alan Stern

>  		return -EOPNOTSUPP;
>  
>  	++fsg->common->ep0_req_tag;	/* Record arrival of a new request */
> -- 
> 2.50.1 (Apple Git-155)
> 
>