linux-kernel - Re: [PATCH 3/6] Drivers: hv: vmbus: Avoid double fetch of payload_size in vmbus_on_msg

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Message-ID: <20201206182038.GC3256@andrea>
Date:   Sun, 6 Dec 2020 19:20:38 +0100
From:   Andrea Parri <parri.andrea@...il.com>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Juan Vazquez <juvazq@...rosoft.com>,
        Saruhan Karademir <skarade@...rosoft.com>
Subject: Re: [PATCH 3/6] Drivers: hv: vmbus: Avoid double fetch of
 payload_size in vmbus_on_msg_dpc()

On Sun, Dec 06, 2020 at 05:14:18PM +0000, Michael Kelley wrote:
> From: Andrea Parri (Microsoft) <parri.andrea@...il.com> Sent: Wednesday, November 18, 2020 6:37 AM
> > 
> > vmbus_on_msg_dpc() double fetches from payload_size.  The double fetch
> > can lead to a buffer overflow when (mem)copying the hv_message object.
> > Avoid the double fetch by saving the value of payload_size into a local
> > variable.
> 
> Similar comment here about providing some brief context in the commit
> message on the problem that we are guarding against by removing the
> double fetch.

Will expand.


> 
> I could see combining this patch with the previous one since the
> motivation and pattern of the changes are exactly the same, just for
> two different fields.

Will consider this suggestion for v3.  Please see v2 for a related
discussion.

  Andrea