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[libvirt] [PATCH] Avoid use of free'd memory in auto destroy callback



From: "Daniel P. Berrange" <berrange redhat com>

The autodestroy callback code has the following function
called from a hash iterator

  qemuDriverCloseCallbackRun(void *payload,
                             const void *name,
                             void *opaque)
  {
    ...
    char *uuidstr = name
    ...

    dom = closeDef->cb(data->driver, dom, data->conn);
    if (dom)
        virObjectUnlock(dom);

    virHashRemoveEntry(data->driver->closeCallbacks, uuidstr);
  }

The closeDef->cb function may well cause the current callback
to be removed, if it shuts down 'dom'. As such the use of
'uuidstr' in virHashRemoveEntry is accessing free'd memory.
We must make a copy of the uuid str before invoking the
callback to be safe.

Signed-off-by: Daniel P. Berrange <berrange redhat com>
---
 src/qemu/qemu_conf.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index b21392e..ee48333 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -510,20 +510,25 @@ qemuDriverCloseCallbackRun(void *payload,
 {
     struct qemuDriverCloseCallbackData *data = opaque;
     qemuDriverCloseDefPtr closeDef = payload;
-    const char *uuidstr = name;
     unsigned char uuid[VIR_UUID_BUFLEN];
+    char uuidstr[VIR_UUID_STRING_BUFLEN];
     virDomainObjPtr dom;
 
     VIR_DEBUG("conn=%p, thisconn=%p, uuid=%s, cb=%p",
-              closeDef->conn, data->conn, uuidstr, closeDef->cb);
+              closeDef->conn, data->conn, (const char *)name, closeDef->cb);
 
     if (data->conn != closeDef->conn || !closeDef->cb)
         return;
 
-    if (virUUIDParse(uuidstr, uuid) < 0) {
-        VIR_WARN("Failed to parse %s", uuidstr);
+    if (virUUIDParse(name, uuid) < 0) {
+        VIR_WARN("Failed to parse %s", (const char *)name);
         return;
     }
+    /* We need to reformat uuidstr, because closeDef->cb
+     * might cause the current hash entry to be removed,
+     * which means 'name' will have been free()d
+     */
+    virUUIDFormat(uuid, uuidstr);
 
     if (!(dom = virDomainFindByUUID(&data->driver->domains, uuid))) {
         VIR_DEBUG("No domain object with UUID %s", uuidstr);
-- 
1.8.1


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