Fix an illegal memory access parsing a corrupt sysroff file.

PR 28564
	* sysdump.c (getCHARS): Check for an out of bounds read.

binutils/sysdump.c

@@ -60,6 +60,12 @@ getCHARS (unsigned char *ptr, int *idx, int size, int max)
       (*idx) += 8;
     }
 
+  if (oc + b > size)
+    {
+      /* PR 28564  */
+      return _("*corrupt*");
+    }
+
   *idx += b * 8;
   r = xcalloc (b + 1, 1);
   memcpy (r, ptr + oc, b);