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

[Ani Sinha <ani@anisinha.ca>]

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On Mon, Oct 12, 2020 at 8:08 PM Ani Sinha <ani@anisinha.ca> wrote:
>
> Request to queue this patch for the next pull.
>
> On Mon, Sep 21, 2020 at 15:03 Ani Sinha <ani@anisinha.ca> wrote:
>>
>> 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
>>