linux-kernel - Re: [PATCH v1] usb: gadget: f_fs: trim extra bytes from USB req

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Message-ID: <2025121718-paltry-caress-43fd@gregkh>
Date: Wed, 17 Dec 2025 14:35:06 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Arseniy Krasnov <avkrasnov@...utedevices.com>
Cc: Akash M <akash.m5@...sung.com>, oxffffaa@...il.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...utedevices.com
Subject: Re: [PATCH v1] usb: gadget: f_fs: trim extra bytes from USB req

On Tue, Dec 09, 2025 at 04:44:11PM +0300, Arseniy Krasnov wrote:
> In '__ffs_epfile_read_data()' number of bytes to copy to user iter is
> returned by USB driver in field 'actual' of structure 'usb_request'
> (see 'ffs_epfile_io_complete()'). Looks like some buggy driver may
> return value larger than actual size of kernel buffer of such USB
> request. This leads to the following crash (produced on 'dwc2' USB
> driver). To prevent this, let's add extra check, which trims reported
> request length.

Why not fix the broken driver instead?  That would resolve this
properly, and not force the gadget code to work around obviously-broken
kernel code.

We try to fix bugs at the root, not paper over them elsewhere.

So what driver is causing this?

thanks,

greg k-h