linux-kernel - Re: [PATCH] USB:bugfix a controller halt error

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Message-ID: <c586a9c4-a51e-b870-c2c3-b0c7ffec0064@suse.com>
Date:   Mon, 24 Jul 2023 14:35:23 +0200
From:   Oliver Neukum <oneukum@...e.com>
To:     Alan Stern <stern@...land.harvard.edu>,
        liulongfang <liulongfang@...wei.com>
Cc:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB:bugfix a controller halt error

On 21.07.23 16:57, Alan Stern wrote:
  
> There is a flaw in your reasoning.
> 
> The operation carried out here is deliberately unsafe (for full-speed
> devices).  It is made before we know the actual maxpacket size for ep0,
> and as a result it might return an error code even when it works okay.
> This shouldn't happen, but a lot of USB hardware is unreliable.
> 
> Therefore we must not ignore the result merely because r < 0.  If we do
> that, the kernel might stop working with some devices.

Right. However, we must make sure we are operating on controlled results.
As is we are operating on a random buffer without checking an IO operation
has been performed on it.

	Regards
		Oliver