linux-kernel - Re: [PATCH net-next] net: usb: aqc111: fix error handling of usbnet read calls

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Message-ID: <39e2951b-6e57-4003-b1c7-c68947f579be@lunn.ch>
Date: Wed, 21 May 2025 14:34:04 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-usb@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzbot+3b6b9ff7b80430020c7b@...kaller.appspotmail.com,
	lvc-project@...uxtesting.org
Subject: Re: [PATCH net-next] net: usb: aqc111: fix error handling of usbnet
 read calls

On Tue, May 20, 2025 at 02:32:39PM +0300, Nikita Zhandarovich wrote:
> Syzkaller, courtesy of syzbot, identified an error (see report [1]) in
> aqc111 driver, caused by incomplete sanitation of usb read calls'
> results. This problem is quite similar to the one fixed in commit
> 920a9fa27e78 ("net: asix: add proper error handling of usb read errors").
> 
> For instance, usbnet_read_cmd() may read fewer than 'size' bytes,
> even if the caller expected the full amount, and aqc111_read_cmd()
> will not check its result properly. As [1] shows, this may lead
> to MAC address in aqc111_bind() being only partly initialized,
> triggering KMSAN warnings.

It looks like __ax88179_read_cmd() has the same issue? Please could
you have a look around and see if more of the same problem exists.

Are there any use cases where usbnet_read_cmd() can actually return
less than size and it not being an error? Maybe this check for ret !=
size can be moved inside usbnet_read_cmd()?

	Andrew