[PATCH v3] qom: code hardening - have bound checking while looping with integer value

[Ani Sinha]

Object property insertion code iterates over an integer to get an unused
index that can be used as an unique name for an object property. This loop
increments the integer value indefinitely. Although very unlikely, this can
still cause an integer overflow.
In this change, we fix the above code by checking against INT16_MAX and making
sure that the interger index does not overflow beyond that value. If no
available index is found, the code would cause an assertion failure. This
assertion failure is necessary because the callers of the function do not check
the return value for NULL.

Signed-off-by: Ani Sinha <ani@anisinha.ca>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 qom/object.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

changelog:
v1: initial version
v2: change INT_MAX to INT16_MAX in code
v3: make the same change in commit log. Sorry for missing it.

diff --git a/qom/object.c b/qom/object.c
index 387efb25eb..9962874598 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1166,11 +1166,11 @@ object_property_try_add(Object *obj, const char *name, 
const char *type,
 
     if (name_len >= 3 && !memcmp(name + name_len - 3, "[*]", 4)) {
         int i;
-        ObjectProperty *ret;
+        ObjectProperty *ret = NULL;
         char *name_no_array = g_strdup(name);
 
         name_no_array[name_len - 3] = '\0';
-        for (i = 0; ; ++i) {
+        for (i = 0; i < INT16_MAX; ++i) {
             char *full_name = g_strdup_printf("%s[%d]", name_no_array, i);
 
             ret = object_property_try_add(obj, full_name, type, get, set,
@@ -1181,6 +1181,7 @@ object_property_try_add(Object *obj, const char *name, 
const char *type,
             }
         }
         g_free(name_no_array);
+        assert(ret);
         return ret;
     }
 
-- 
2.17.1