linux-kernel - Re: [PATCH v1 4/6] virtio console: Harden control message handling

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Message-ID: <Y8lgIS+jygB7SGrn@kroah.com>
Date:   Thu, 19 Jan 2023 16:22:09 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     mst@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, elena.reshetova@...el.com,
        kirill.shutemov@...ux.intel.com, Amit Shah <amit@...nel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v1 4/6] virtio console: Harden control message handling

On Thu, Jan 19, 2023 at 03:57:19PM +0200, Alexander Shishkin wrote:
> In handle_control_message(), we look at the ->event field twice, which
> gives a malicious VMM a window in which to switch it from PORT_ADD to
> PORT_REMOVE, triggering a null dereference further down the line:

How is the other VMM have full control over the full message here?
Shouldn't this all have been copied into our local memory if we are
going to be poking around in it?  Like I mentioned in my other review,
copy it all once and then parse it.  Don't try to mess with individual
fields one at a time otherwise that way lies madness...

thanks,

greg k-h