security: don't treat structure as an array of struct hlist_head

The initialization of "security_hook_heads" is done by casting it to
another structure pointer type, and treating it as an array of "struct
hlist_head" objects. This requires an exception be made in "randstruct",
because otherwise it will emit an error, reducing the effectiveness of
the hardening technique.

Instead of using a cast, initialize the individual struct hlist_head
elements in security_hook_heads explicitly. This removes the need for
the cast and randstruct exception.

Signed-off-by: Bill Wendling <morbo@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220407175930.471870-1-morbo@google.com

diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
index 334741a..c2ec81b 100644 (file)
--- a/scripts/gcc-plugins/randomize_layout_plugin.c
+++ b/scripts/gcc-plugins/randomize_layout_plugin.c
@@ -52,8 +52,6 @@ static const struct whitelist_entry whitelist[] = {
        { "net/unix/af_unix.c", "unix_skb_parms", "char" },
        /* big_key payload.data struct splashing */
        { "security/keys/big_key.c", "path", "void *" },
-       /* walk struct security_hook_heads as an array of struct hlist_head */
-       { "security/security.c", "hlist_head", "security_hook_heads" },
        { }
 };
 

diff --git a/security/security.c b/security/security.c
index b7cf5cb..37a9eeb 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -365,13 +365,12 @@ static void __init ordered_lsm_init(void)
 
 int __init early_security_init(void)
 {
-       int i;
-       struct hlist_head *list = (struct hlist_head *) &security_hook_heads;
        struct lsm_info *lsm;
 
-       for (i = 0; i < sizeof(security_hook_heads) / sizeof(struct hlist_head);
-            i++)
-               INIT_HLIST_HEAD(&list[i]);
+#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
+       INIT_HLIST_HEAD(&security_hook_heads.NAME);
+#include "linux/lsm_hook_defs.h"
+#undef LSM_HOOK
 
        for (lsm = __start_early_lsm_info; lsm < __end_early_lsm_info; lsm++) {
                if (!lsm->enabled)