genksyms: fix memory leak when the same symbol is read from *.symref file

When a symbol that is already registered is read again from *.symref
file, __add_symbol() removes the previous one from the hash table without
freeing it.

[Test Case]

  $ cat foo.c
  #include <linux/export.h>
  void foo(void);
  void foo(void) {}
  EXPORT_SYMBOL(foo);

  $ cat foo.symref
  foo void foo ( void )
  foo void foo ( void )

When a symbol is removed from the hash table, it must be freed along
with its ->name and ->defn members. However, sym->name cannot be freed
because it is sometimes shared with node->string, but not always. If
sym->name and node->string share the same memory, free(sym->name) could
lead to a double-free bug.

To resolve this issue, always assign a strdup'ed string to sym->name.

Fixes: 64e6c1e12372 ("genksyms: track symbol checksum changes")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/scripts/genksyms/parse.y b/scripts/genksyms/parse.y
index 840371d01bf4..689cb6bb40b6 100644
--- a/scripts/genksyms/parse.y
+++ b/scripts/genksyms/parse.y
@@ -482,12 +482,12 @@ enumerator_list:
 enumerator:
 	IDENT
 		{
-			const char *name = strdup((*$1)->string);
+			const char *name = (*$1)->string;
 			add_symbol(name, SYM_ENUM_CONST, NULL, 0);
 		}
 	| IDENT '=' EXPRESSION_PHRASE
 		{
-			const char *name = strdup((*$1)->string);
+			const char *name = (*$1)->string;
 			struct string_list *expr = copy_list_range(*$3, *$2);
 			add_symbol(name, SYM_ENUM_CONST, expr, 0);
 		}