Commit be2fa44b authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

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: 64e6c1e1 ("genksyms: track symbol checksum changes")
Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
parent 45c9c410

scripts/genksyms/genksyms.c

+6 −2
Original line number Diff line number Diff line
@@ -272,11 +272,15 @@ static struct symbol *__add_symbol(const char *name, enum symbol_type type, 
				break;

			}

		}



		free_list(sym->defn, NULL);

		free(sym->name);

		free(sym);

		--nsyms;

	}



	sym = xmalloc(sizeof(*sym));

	sym->name = name;

	sym->name = xstrdup(name);

	sym->type = type;

	sym->defn = defn;

	sym->expansion_trail = NULL;
@@ -483,7 +487,7 @@ static void read_reference(FILE *f) 
			defn = def;

			def = read_node(f);

		}

		subsym = add_reference_symbol(xstrdup(sym->string), sym->tag,

		subsym = add_reference_symbol(sym->string, sym->tag,

					      defn, is_extern);

		subsym->is_override = is_override;

		free_node(sym);

scripts/genksyms/genksyms.h

+1 −1
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ struct string_list { 


struct symbol {

	struct symbol *hash_next;

	const char *name;

	char *name;

	enum symbol_type type;

	struct string_list *defn;

	struct symbol *expansion_trail;

scripts/genksyms/parse.y

+2 −2
Original line number Diff line number Diff line
@@ -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);

		}