Re: [Xen-devel] [PATCH for stable 3.10] xen-netback: drop SKB from internal queue if frontend is disconnected

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jul 11, 2014 at 02:15:29PM +0100, Ian Campbell wrote:
> On Fri, 2014-07-11 at 14:08 +0100, Wei Liu wrote:
> > In 88a810def7 ("xen-netback: fix refcnt unbalance for 3.10"), we moved
> > the ref counting code from xenvif_disconnect to xenvif_free.
> 
> Since this was a 3.10 specific backport that explains why this is also
> such?
> 

Yes.

> > It can occur that frontend is disconnected while there's still SKB
> > stuck in netback's rx_queue in rare case. When netback thread wakes up,
> > it will try to write to an already unmapped ring, resulting in kernel
> > oops.
> > 
> > Moving the ref counting back to xenvif_disconnect isn't an option as it
> > reintroduces an old bug. Further more, writing into a dead frontend's
> > ring and memory is just wrong. Dropping those SKBs seems to be a good
> > strategy.
> > 
> > This patch fixes that corner case: introduce a flag to indicate whether
> > frontend ring is mapped. If the ring is unmapped, just drop those SKBs.
> > 
> > This bug only manifests in 3.10 kernel. Kernel >=3.12 doesn't have it.
> 
> What about 3.11?
> 

3.11 is long dead while 3.10 is LTS kernel. I don't think GregKH accepts
patch for 3.11 anymore.

Wei.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel