linux-kernel - Re: [PATCH 4/6] Drivers: hv: vmbus: Avoid use-after-free in vmbus_onoffer

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Message-ID: <20201124195407.GA16042@andrea>
Date:   Tue, 24 Nov 2020 20:54:07 +0100
From:   Andrea Parri <parri.andrea@...il.com>
To:     Wei Liu <wei.liu@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        "K . Y . Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        linux-hyperv@...r.kernel.org,
        Michael Kelley <mikelley@...rosoft.com>,
        Juan Vazquez <juvazq@...rosoft.com>,
        Saruhan Karademir <skarade@...rosoft.com>
Subject: Re: [PATCH 4/6] Drivers: hv: vmbus: Avoid use-after-free in
 vmbus_onoffer_rescind()

On Tue, Nov 24, 2020 at 04:26:33PM +0000, Wei Liu wrote:
> On Wed, Nov 18, 2020 at 03:36:47PM +0100, Andrea Parri (Microsoft) wrote:
> > When channel->device_obj is non-NULL, vmbus_onoffer_rescind() could
> > invoke put_device(), that will eventually release the device and free
> > the channel object (cf. vmbus_device_release()).  However, a pointer
> > to the object is dereferenced again later to load the primary_channel.
> > The use-after-free can be avoided by noticing that this load/check is
> > redundant if device_obk is non-NULL: primary_channel must be NULL if
> 
> device_obk -> device_obj

Fixed.


> 
> > device_obj is non-NULL, cf. vmbus_add_channel_work().
> > 
> 
> Missing a Fixes tag?

Yes, I've added the tag.

Thanks,
  Andrea