Fix for PR70481 Libiberty Demangler

[Marcel Böhme]

Hi,

This fixes the use-after-free detailed in 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70481

There is a variable ksize storing the amount of allocated memory for the array 
ktypevec. ksize being zero (0) indicates that some memory must be allocated 
upon the first write. When more memory is needed, both ksize and the memory are 
doubled during reallocation. At some point the memory for the array is freed 
(in squangle_mop_up) but the value of ksize remains. Since ksize is not 0, 
there is no indication that new memory must be allocated when there is another 
write to the array.

The same holds for bsize and btypevec.

Best regards,
- Marcel


Index: libiberty/cplus-dem.c
===================================================================
--- libiberty/cplus-dem.c       (revision 234607)
+++ libiberty/cplus-dem.c       (working copy)
@@ -1237,11 +1237,13 @@  squangle_mop_up (struct work_stuff *work)
     {
       free ((char *) work -> btypevec);
       work->btypevec = NULL;
+      work->bsize = 0;
     }
   if (work -> ktypevec != NULL)
     {
       free ((char *) work -> ktypevec);
       work->ktypevec = NULL;
+      work->ksize = 0;
     }
 }