libxc: limit cpu values when setting vcpu affinity

Enterprise / Virtualization / Xen - Ian Jackson [eu.citrix.com] - 29 May 2013 09:49 EDT

When support for pinning more than 64 cpus was added, check for cpu out-of-range values was removed. This can lead to subsequent out-of-bounds cpumap array accesses in case the cpu number is higher than the actual count.

This patch returns the check.

This is CVE-2013-2072 / XSA-56

###

diff --git a/tools/python/xen/lowlevel/xc/xc.c b/tools/python/xen/lowlevel/xc/xc.c
index e220f68..e611b24 100644
--- a/tools/python/xen/lowlevel/xc/xc.c
+++ b/tools/python/xen/lowlevel/xc/xc.c
@@ -228,6 +228,7 @@ static PyObject *pyxc_vcpu_setaffinity(XcObject *self,
int vcpu = 0, i;
xc_cpumap_t cpumap;
PyObject *cpulist = NULL;
+ int nr_cpus;

static char *kwd_list[] = { "domid", "vcpu", "cpumap", NULL };

@@ -235,6 +236,10 @@ static PyObject *pyxc_vcpu_setaffinity(XcObject *self,
&dom, &vcpu, &cpulist) )
return NULL;

+ nr_cpus = xc_get_max_cpus(self->xc_handle);
+ if ( nr_cpus == 0 )
+ return pyxc_error_to_exception(self->xc_handle);
+
cpumap = xc_cpumap_alloc(self->xc_handle);
if(cpumap == NULL)
return pyxc_error_to_exception(self->xc_handle);
@@ -244,6 +249,13 @@ static PyObject *pyxc_vcpu_setaffinity(XcObject *self,
for ( i = 0; i < PyList_Size(cpulist); i++ )
{
long cpu = PyInt_AsLong(PyList_GetItem(cpulist, i));
+ if ( cpu < 0 || cpu >= nr_cpus )
+ {
+ free(cpumap);
+ errno = EINVAL;
+ PyErr_SetFromErrno(xc_error_obj);
+ return NULL;
+ }
cpumap[cpu / 8] |= 1 << (cpu % 8);
}
}

41abbad libxc: limit cpu values when setting vcpu affinity
tools/python/xen/lowlevel/xc/xc.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

Upstream: xenbits.xen.org


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