Re: [Xen-devel] [PATCH] xen/netback: Fix null-pointer access in netback_uevent

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Thu, 2010-07-29 at 13:42 +0100, Bastian Blank wrote:
> On Thu, Jul 29, 2010 at 12:47:15PM +0100, Ian Campbell wrote:
> > On Wed, 2010-07-28 at 17:20 +0100, Bastian Blank wrote:
> > > 78b55f90e72348e231092dbe3e50ac7414b9e1af still fails:
> > > | BUG: unable to handle kernel NULL pointer dereference at 
> > > 0000000000000150
> > > | IP: [<ffffffff81200764>] netback_uevent+0x8c/0xb9
> > I tried to reproduce this on squeeze (installed this morning) but
> > without luck. I'm running on amd64 with the hypervisor and tools from
> > squeeze and your
> > linux-image-2.6.32-5-xen-amd64_2.6.32-19~xen.2_amd64.deb test package
> > (md5 e3bb29be9588fa75b7740c046352b15b).
> 
> Its a race condition, so you may or may not see it. It is rather good
> reproducible on my test machine with 12 cores and a lot of guest
> creations running at once (32 to be exact in my case).

Thanks, looks like I need to get much more aggressive then.

> > Did you apply a fix/workaround to your package?
> 
> Yes, this is included since 2.6.32-15.

The patch from <20100529184452.GA18365@xxxxxxxxxxxxxxxxxxxxxxx>?

I think the only reason this hasn't gone in already are the additional
concerns which Jan raised in
<4C0383670200007800004B63@xxxxxxxxxxxxxxxxxx>. 

You may be inteested in the patch attached to
http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1612

Jeremy, given that Bastian's patch seems to help and is correct, if
potentially incomplete, perhaps we should put it in now rather than
waiting for the complete fix?

> >                                                 I'm about to try with a
> > pristine 78b55f90e72348e231092dbe3e50ac7414b9e1af from xen.git but any
> > tips on reproducing gratefully accepted.
> 
> Try linux-image-2.6.32-5-xen-amd64_2.6.32-19~xen.1_amd64.deb, the only
> difference to the newer is that the fix is again included.

I'll try that. Thanks.

Ian.



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