RFR JDK-8007609

[Chris Hegarty]

On 02/07/2013 11:54 AM, David Holmes wrote:
> ....
>> AFAICS setting len=0 means len==0 will be true and so we will
>> free(result).
>
> And if len != 0 then we will have already freed result, so avoiding a
> double-free.

Here's the code as it stands today.


  113     result = (WCHAR*)malloc(MAX_PATH * sizeof(WCHAR));
  114     if (result != NULL) {
  115         DWORD len = (*GetFinalPathNameByHandle_func)(h, result, 
MAX_PATH, 0);
  116         if (len >= MAX_PATH) {
  117             /* retry with a buffer of the right size */
  118             result = (WCHAR*)realloc(result, (len+1) * sizeof(WCHAR));
  119             if (result != NULL) {
  120                 len = (*GetFinalPathNameByHandle_func)(h, result, 
len, 0);
  121             } else {
  122                 len = 0;
  123             }
  124         }
  125         if (len > 0) {
  126             /**
  127              * Strip prefix (should be \\?\ or \\?\UNC)
  128              */
  129             if (result[0] == L'\\' && result[1] == L'\\' &&
  130                 result[2] == L'?' && result[3] == L'\\')
  131             {
  132                 int isUnc = (result[4] == L'U' &&
  133                              result[5] == L'N' &&
  134                              result[6] == L'C');
  135                 int prefixLen = (isUnc) ? 7 : 4;
  136                 /* actual result length (includes terminator) */
  137                 int resultLen = len - prefixLen + (isUnc ? 1 : 0) + 1;
  138
  139                 /* copy result without prefix into new buffer */
  140                 WCHAR *tmp = (WCHAR*)malloc(resultLen * 
sizeof(WCHAR));
  141                 if (tmp == NULL) {
  142                     len = 0;          <<<<<<<<<<<<<<<<<<< HERE
  143                 } else {
  144                     WCHAR *p = result;
  145                     p += prefixLen;
  146                     if (isUnc) {
  147                         WCHAR *p2 = tmp;
  148                         p2[0] = L'\\';
  149                         p2++;
  150                         wcscpy(p2, p);
  151                     } else {
  152                         wcscpy(tmp, p);
  153                     }
  154                     free(result);
  155                     result = tmp;
  156                 }
  157             }
  158         }
  159
  160         /* unable to get final path */
  161         if (len == 0 && result != NULL) {
  162             free(result);
  163             result = NULL;
  164         }
  165     }

-Chris.