linux-kernel - Re: [PATCH v2 0/3] xen: harden blkfront against malicious backends

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Date:   Thu, 8 Jul 2021 10:22:31 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     xen-devel@...ts.xenproject.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Roger Pau Monné <roger.pau@...rix.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH v2 0/3] xen: harden blkfront against malicious backends

On Thu, Jul 08, 2021 at 02:43:42PM +0200, Juergen Gross wrote:
> Xen backends of para-virtualized devices can live in dom0 kernel, dom0
> user land, or in a driver domain. This means that a backend might
> reside in a less trusted environment than the Xen core components, so
> a backend should not be able to do harm to a Xen guest (it can still
> mess up I/O data, but it shouldn't be able to e.g. crash a guest by
> other means or cause a privilege escalation in the guest).
> 
> Unfortunately blkfront in the Linux kernel is fully trusting its
> backend. This series is fixing blkfront in this regard.
> 
> It was discussed to handle this as a security problem, but the topic
> was discussed in public before, so it isn't a real secret.

Wow. This looks like what Marek did .. in 2018!

https://lists.xenproject.org/archives/html/xen-devel/2018-04/msg02336.html

Would it be worth crediting Marek?
> 
> Changes in V2:
> - put blkfront patches into own series
> - some minor comments addressed
> 
> Juergen Gross (3):
>   xen/blkfront: read response from backend only once
>   xen/blkfront: don't take local copy of a request from the ring page
>   xen/blkfront: don't trust the backend response data blindly
> 
>  drivers/block/xen-blkfront.c | 122 +++++++++++++++++++++++------------
>  1 file changed, 80 insertions(+), 42 deletions(-)
> 
> -- 
> 2.26.2
>