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>

diff --git a/scripts/genksyms/genksyms.c b/scripts/genksyms/genksyms.c
index 8ca46f807b57aacec3a6b244384f033e102052c5..c5e8e0e0f94906590d3c16de0324014327126aad 100644 (file)
--- a/scripts/genksyms/genksyms.c
+++ b/scripts/genksyms/genksyms.c
@@ -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);

diff --git a/scripts/genksyms/genksyms.h b/scripts/genksyms/genksyms.h
index 21ed2ec2d98ca8cdc6fe7bf28000d5d5fc7bf528..5621533dcb8e4302dcbd4b2e333c2083e67cdc59 100644 (file)
--- a/scripts/genksyms/genksyms.h
+++ b/scripts/genksyms/genksyms.h
@@ -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;

diff --git a/scripts/genksyms/parse.y b/scripts/genksyms/parse.y
index 840371d01bf4862c2899e6910051ec28ec04551c..689cb6bb40b657e4d4e6c3948d70569256ac9275 100644 (file)
--- 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);
                }