[libvirt] [PATCH] qemu: Fix two issues in qemuDomainSetVcpus error handling

[John Ferlan]

Issue #1 - A call to virBitmapNew did not check if the allocation
failed which could lead to a NULL dereference

Issue #2 - When deleting the pin entries from the config file, the
code loops from the number of elements down to the "new" vcpu count;
however, the pin id values are numbered 0..n-1 not 1..n, so the "first"
pin attempt would never work. Luckily the check was for whether the
incoming 'n' (vcpu id) matched the entry in the array from 0..arraysize
rather than a dereference of the 'n' entry

Signed-off-by: John Ferlan <jferlan at redhat.com>
---

NOTE: These were found on inspection while working/debugging the a IOThreads
series which borrows from the SetVcpus code.  I can separate the two if
desired, but I think the second issue is mostly an optimization.


 src/qemu/qemu_driver.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index ed6764d..6d9217b 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4752,7 +4752,11 @@ static int qemuDomainHotplugVcpus(virQEMUDriverPtr driver,
                 if (VIR_ALLOC(vcpupin) < 0)
                     goto cleanup;
 
-                vcpupin->cpumask = virBitmapNew(VIR_DOMAIN_CPUMASK_LEN);
+                if (!(vcpupin->cpumask =
+                      virBitmapNew(VIR_DOMAIN_CPUMASK_LEN))) {
+                    VIR_FREE(vcpupin);
+                    goto cleanup;
+                }
                 virBitmapCopy(vcpupin->cpumask, vm->def->cpumask);
                 vcpupin->id = i;
                 if (VIR_APPEND_ELEMENT_COPY(vm->def->cputune.vcpupin,
@@ -4987,7 +4991,7 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
         if (flags & VIR_DOMAIN_AFFECT_CONFIG) {
             /* remove vcpupin entries for vcpus that were unplugged */
             if (nvcpus < persistentDef->vcpus) {
-                for (i = persistentDef->vcpus; i >= nvcpus; i--)
+                for (i = persistentDef->vcpus - 1; i >= nvcpus; i--)
                     virDomainPinDel(&persistentDef->cputune.vcpupin,
                                     &persistentDef->cputune.nvcpupin,
                                     i);
-- 
2.1.0