Keep a local copy of the symbol name in the symbol table

The symbol_header structure that tracks symbols with a particular name
may have a different (longer) life time than the symbols it tracks.
Not keeping a local copy of the name can lead to use-after-free
errors.  For example, the following sequence would trigger such an
error:

    char *copy = strdup(name);

    _mesa_symbol_table_push_scope(st);
    _mesa_symbol_table_add_symbol(st, 0, name, NULL);
    _mesa_symbol_table_pop_scope(st);
    free(name);
    _mesa_symbol_table_find_symbol(st, 0, copy);

With this change, the symbol table keeps a local copy of the name that
has the same life time as the symbol_header for that name.  This
resolves some use-after-free errors with built-in functions in the
GLSL compiler.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/mesa/program/symbol_table.c b/src/mesa/program/symbol_table.c
index 3fea5ee1f1f..09e7cb44ef3 100644
--- a/src/mesa/program/symbol_table.c
+++ b/src/mesa/program/symbol_table.c
@@ -75,7 +75,7 @@ struct symbol_header {
     struct symbol_header *next;
 
     /** Symbol name. */
-    const char *name;
+    char *name;
 
     /** Linked list of symbols with the same name. */
     struct symbol *symbols;
@@ -337,9 +337,9 @@ _mesa_symbol_table_add_symbol(struct _mesa_symbol_table *table,
 
     if (hdr == NULL) {
         hdr = calloc(1, sizeof(*hdr));
-        hdr->name = name;
+        hdr->name = strdup(name);
 
-        hash_table_insert(table->ht, hdr, name);
+        hash_table_insert(table->ht, hdr, hdr->name);
 	hdr->next = table->hdr;
 	table->hdr = hdr;
     }
@@ -404,6 +404,7 @@ _mesa_symbol_table_dtor(struct _mesa_symbol_table *table)
 
    for (hdr = table->hdr; hdr != NULL; hdr = next) {
        next = hdr->next;
+       free(hdr->name);
        free(hdr);
    }