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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 01/04/2012 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

numa_mode      : strict
numa_nodeset   : 0-1


numa_mode      : strict
numa_nodeset   : 0-2


numa_mode      : strict
numa_nodeset   : 0-3


numa_mode      : strict
numa_nodeset   : 0-4


numa_mode      : strict
numa_nodeset   : 0-5


numa_mode      : strict
numa_nodeset   : 0-6


numa_mode      : strict
numa_nodeset   : 0-7


numa_mode      : strict
numa_nodeset   : 0-8


numa_mode      : strict
numa_nodeset   : 0-9


numa_mode      : strict
numa_nodeset   : 0-10

                                           VIR_DOMAIN_CPUMASK_LEN)<   0) {
-                    memcpy(persistentDef->numatune.memory.nodemask,
-                           oldnodemask, VIR_DOMAIN_CPUMASK_LEN);
+                    memcpy(params[i].value.s, oldnodemask, VIR_DOMAIN_CPUMASK_LEN);
                      ret = -1;
                      continue;
                  }
 From f2fe7c7d0041779895330416dca6ac97fcbec88a Mon Sep 17 00:00:00 2001
From: Hu Tao<hutao cn fujitsu com>
Date: Wed, 4 Jan 2012 17:00:27 +0800
Subject: [PATCH] qemu: fix a bug in numatune

When setting numa nodeset for a domain which has no nodeset set
before, libvirtd crashes by dereferring the pointer to the old
nodemask which is null in the case.
---
  src/qemu/qemu_driver.c |   22 ++++++++++++++++++----
  1 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 82bab67..37330b4 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -6721,14 +6721,28 @@ qemuDomainSetNumaParameters(virDomainPtr dom,
              }

              if (flags&   VIR_DOMAIN_AFFECT_CONFIG) {
-                memcpy(oldnodemask, persistentDef->numatune.memory.nodemask,
-                       VIR_DOMAIN_CPUMASK_LEN);
+                bool savedmask = false;
+                if (!persistentDef->numatune.memory.nodemask) {
+                    if (VIR_ALLOC_N(persistentDef->numatune.memory.nodemask,
+                                    VIR_DOMAIN_CPUMASK_LEN)<   0) {
+                        virReportOOMError();
+                        ret = -1;
+                        goto cleanup;
+                    }
+                } else {
+                    memcpy(oldnodemask, persistentDef->numatune.memory.nodemask,
+                           VIR_DOMAIN_CPUMASK_LEN);
+                    savedmask = true;
+                }
                  if (virDomainCpuSetParse(params[i].value.s,
                                           0,
                                           persistentDef->numatune.memory.nodemask,
                                           VIR_DOMAIN_CPUMASK_LEN)<   0) {
-                    memcpy(persistentDef->numatune.memory.nodemask,
-                           oldnodemask, VIR_DOMAIN_CPUMASK_LEN);
+                    if (savedmask)
+                        memcpy(persistentDef->numatune.memory.nodemask,
+                               oldnodemask, VIR_DOMAIN_CPUMASK_LEN);
+                    else
+                        VIR_FREE(persistentDef->numatune.memory.nodemask);
Oops. The same should be done when --live.

                      ret = -1;
                      continue;
                  }


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