[Qemu-devel] [PATCH v2] pc-dimm: fix error handling in pc_dimm_check_memdev_is_busy()

[Igor Mammedov <imammedo@redhat.com>]

If host_memory_backend_get_memory() were to return error and
NULL MemoryRegion, pc_dimm_check_memdev_is_busy() would crash
dereferencing NULL pointer in memory_region_is_mapped().
But if error is set and non NULL MemoryRegion is returned
then error_setg() will fail with "error already set" assertion
in error_setv()

To avoid above issues use typical error handling pattern
for property setters:

Error *local_error = NULL;
...
error_propagate(errp, local_err);

Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
---
 hw/mem/pc-dimm.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
index 650f0f8..973bf20 100644
--- a/hw/mem/pc-dimm.c
+++ b/hw/mem/pc-dimm.c
@@ -364,15 +364,22 @@ static void pc_dimm_check_memdev_is_busy(Object *obj, const char *name,
                                       Object *val, Error **errp)
 {
     MemoryRegion *mr;
+    Error *local_err = NULL;
 
-    mr = host_memory_backend_get_memory(MEMORY_BACKEND(val), errp);
+    mr = host_memory_backend_get_memory(MEMORY_BACKEND(val), &local_err);
+    if (local_err) {
+        goto out;
+    }
     if (memory_region_is_mapped(mr)) {
         char *path = object_get_canonical_path_component(val);
-        error_setg(errp, "can't use already busy memdev: %s", path);
+        error_setg(&local_err, "can't use already busy memdev: %s", path);
         g_free(path);
     } else {
-        qdev_prop_allow_set_link_before_realize(obj, name, val, errp);
+        qdev_prop_allow_set_link_before_realize(obj, name, val, &local_err);
     }
+
+out:
+    error_propagate(errp, local_err);
 }
 
 static void pc_dimm_init(Object *obj)
-- 
1.8.3.1