Problem with id when mgetgroups returns no groups.

[scott . gnu . 2009]

All,

In coreutils 8.1, src/id.c line 296:

         gid_t *groups;
         int i;

         int n_groups = mgetgroups (username, (pwd ? pwd->pw_gid : (gid_t) -1),
                                                                                 
&groups);
         if (n_groups < 0 && errno != ENOSYS)
                {
                  if (username)
                         {
                                error (0, errno, _("failed to get groups for user 
%s"),
                                                 quote (username));
                         }
                  else
                         {
				error (0, errno, _("failed to get groups for the current 
process"));
                         }
                  ok = false;
                  return;
                }

         if (n_groups > 0)
                fputs (_(" groups="), stdout);
         for (i = 0; i < n_groups; i++)
                {
                  if (i > 0)
                         putchar (',');
                  printf ("%lu", (unsigned long int) groups[i]);
                  grp = getgrgid (groups[i]);
                  if (grp)
                         printf ("(%s)", grp->gr_name);
                }
         free (groups);

if mgetgroups doesn't find any groups, "groups" will not be changed and 
therefore still contain an uninitialised value which is later freed on the 
last line of this extract.  The fix we have here is to initialise groups to 
NULL, then test before we free (although with glibc that isn't actually 
necessary).

Thought you might like to know.

Scott.