netdev - malicious devices causing unaligned accesses

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Date:   Thu, 17 Feb 2022 09:39:17 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     stern@...land.harvard.edu, USB list <linux-usb@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Giuliano Belinassi <giuliano.belinassi@...e.com>,
        Bjørn Mork <bjorn@...k.no>
Subject: malicious devices causing unaligned accesses

Hi,

going through the USB network drivers looking for ways
a malicious device could do us harm I found drivers taking
the alignment coming from the device for granted.

An example can be seen in qmi_wwan:

while (offset + qmimux_hdr_sz < skb->len) { hdr = (struct qmimux_hdr
*)(skb->data + offset); len = be16_to_cpu(hdr->pkt_len); As you can see
the driver accesses stuff coming from the device with the expectation
that it keep to natural alignment. On some architectures that is a way a
device could use to do bad things to a host. What is to be done about
that? Regards Oliver