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Date:   Mon, 24 Jul 2023 14:35:23 +0200
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Subject: Re: [PATCH] USB:bugfix a controller halt error
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To:     Alan Stern <stern@rowland.harvard.edu>,
        liulongfang <liulongfang@huawei.com>
Cc:     gregkh@linuxfoundation.org, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20230721100015.27124-1-liulongfang@huawei.com>
 <c3ab029f-f6ab-4b09-b2b5-1cc6a5370d0d@rowland.harvard.edu>
From:   Oliver Neukum <oneukum@suse.com>
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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