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Re: [libvirt] [PATCH] qemu: fix a bug in numatune (was Re: [PATCH] qemu: Prevent crash of libvirtd when setting numa parameters)



On 01/05/2012 09:12 AM, Hu Tao wrote:
On Wed, Jan 04, 2012 at 05:56:21PM +0800, Alex Jia wrote:
On 01/04/2012 05:28 PM, Hu Tao wrote:
On Wed, Jan 04, 2012 at 05:15:24PM +0800, Alex Jia wrote:
On 01/04/2012 05:04 PM, Hu Tao wrote:
On Wed, Jan 04, 2012 at 03:53:19PM +0800, ajia redhat com wrote:
From: Alex Jia<ajia redhat com>

It's a NULL pointer deref issue, which leads to libvirtd crash. This patch
directly use 'params[i].value.s' value instead of derefing a NULL pointer
on memcpy.

* how to reproduce?
% virsh numatune<domain>    --nodeset 0
The domain must have no nodeset set previously (to crash in this example).

% service libvirtd status

* src/qemu/qemu_driver.c (qemuDomainSetNumaParameters): avoid a NULL pointer deref.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=771562

Signed-off-by: Alex Jia<ajia redhat com>
---
  src/qemu/qemu_driver.c |    6 ++----
  1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 82bab67..1bd93f6 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -6721,14 +6721,12 @@ qemuDomainSetNumaParameters(virDomainPtr dom,
              }

              if (flags&    VIR_DOMAIN_AFFECT_CONFIG) {
-                memcpy(oldnodemask, persistentDef->numatune.memory.nodemask,
-                       VIR_DOMAIN_CPUMASK_LEN);
+                memcpy(oldnodemask, params[i].value.s, VIR_DOMAIN_CPUMASK_LEN);
                  if (virDomainCpuSetParse(params[i].value.s,
                                           0,
                                           persistentDef->numatune.memory.nodemask,
Not correct. In this case persistentDef->numatune.memory.nodemask is
null, and virDomainCpuSetParse will always fail, thus the nodeset will
never be set.
In fact, I can successfully set nodeset value:

# virsh numatune foo --nodeset 0-1

# virsh numatune foo
numa_mode      : strict
numa_nodeset   : 0-1
Weird. I've never succeeded with your patch. Can you double-check again?
Hu Tao, Indeed, it's weird. the patch always works well for me:

# for i in $(seq 10); do virsh numatune foo --nodeset 0-$i; virsh
numatune foo; done
Can you test as the following steps?

1. remove numatune element from the dom's xml.
2. restart libvirtd
3. set numa nodeset (say, virsh numatune dom --nodeset 0-2)
Yeah, you're right, I need to cleanup previous <numatune> element block from guest, and your patch '[PATCHv2] qemu: fix a bug in numatune' works well for me.

Thanks for your comment,
Alex


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