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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2010-07-28 at 17:20 +0100, Bastian Blank wrote:
> On Mon, May 31, 2010 at 09:07:04AM +0100, Jan Beulich wrote:
> > >>> On 31.05.10 at 09:37, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
> > > Furthermore, the backend creation patch also needs adjustment,
> > ... path ...
> > > as it currently stores a non-NULL non-pointer value in be->netif if
> > > netif_alloc() fails. To require the sysfs path to use IS_ERR() on
> > ... To *not* require ...
> > > be->netif, I think netif_alloc()'s result should be stored to a local 
> > > variable first and only written to be->netif when valid.
>  
> 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).

I tried pulling in the udev from sid too (since I think udev version has
been implicated in triggering this issue) but that didn't help
reproduce.

Did you apply a fix/workaround to your package? I'm about to try with a
pristine 78b55f90e72348e231092dbe3e50ac7414b9e1af from xen.git but any
tips on reproducing gratefully accepted.

My test VM is running the Lenny installer with the following cfg:

Ian.

#  -*- mode: python; -*-
vcpus = 2

memory = 128

name = "d32-1"
vif = [ 'mac=00:16:3e:72:42:06' ]
disk = ['file:/vm/debian-x86_32-1.img,xvda,w']

hostname = "debian-1"

tsc_mode=2
extra = "xencons=hvc console=hvc0 ro root=/dev/xvda1" #

# Install...
extra = "debian-installer/exit/always_halt=true -- " + extra + " 
auto-install/enable=true hostname=d32-1 domain=uk.xensource.com 
url=http://cosworth/users/ianc/ks/lenny.cfg";
kernel = "/scratch/lenny/i386/vmlinuz"
ramdisk = "/scratch/lenny/i386/initrd.gz"

on_crash = "coredump-destroy"
on_reboot = "restart"



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