Re: [Qemu-stable] [2.2 PATCH V2 for-4.5] virtio-net: fix unmap leak

[Stefano Stabellini]

On Thu, 27 Nov 2014, Konrad Rzeszutek Wilk wrote:
> On Nov 27, 2014 7:46 AM, Stefano Stabellini <address@hidden> wrote:
> >
> > Konrad, I think we should have this fix in 4.5: without it 
> > vif=[ 'model=virtio-net' ] crashes QEMU. 
> >
> 
> Is it an regression?

Good question: I was trying to investigate that.

virtio-net is currently *not* documented in the xl interface:


### model

This keyword is valid for HVM guest devices with `type=ioemu` only.

Specifies the type device to emulated for this guest. Valid values
are:

  * `rtl8139` (default) -- Realtek RTL8139
  * `e1000` -- Intel E1000 
  * in principle any device supported by your device model


The last working version of virtio-net on Xen is QEMU v1.4.0. That means
that the bug affects Xen 4.4 too (but it should work in Xen 4.3).


> > On Thu, 27 Nov 2014, Peter Maydell wrote: 
> > > On 27 November 2014 at 12:33, Michael S. Tsirkin <address@hidden> wrote: 
> > > > On Thu, Nov 27, 2014 at 06:04:03PM +0800, Jason Wang wrote: 
> > > >> virtio_net_handle_ctrl() and other functions that process control vq 
> > > >> request call iov_discard_front() which will shorten the iov. This will 
> > > >> lead unmapping in virtqueue_push() leaks mapping. 
> > > >> 
> > > >> Fixes this by keeping the original iov untouched and using a temp 
> > > >> variable 
> > > >> in those functions. 
> > > >> 
> > > >> Cc: Wen Congyang <address@hidden> 
> > > >> Cc: Stefano Stabellini <address@hidden> 
> > > >> Cc: address@hidden 
> > > >> Signed-off-by: Jason Wang <address@hidden> 
> > > > 
> > > > Reviewed-by: Michael S. Tsirkin <address@hidden> 
> > > > 
> > > > Peter, can you pick this up or do you want a pull request? 
> > > 
> > > I can pick it up. I was waiting a bit to check that everybody 
> > > was happy that this is the correct way to fix the bug and the 
> > > patch is ok... 
>