apparmor: Refactor to remove bprm_secureexec hook

The AppArmor bprm_secureexec hook can be merged with the bprm_set_creds
hook since it's dealing with the same information, and all of the details
are finalized during the first call to the bprm_set_creds hook via
prepare_binprm() (subsequent calls due to binfmt_script, etc, are ignored
via bprm->called_set_creds).

Here, all the comments describe how secureexec is actually calculated
during bprm_set_creds, so this actually does it, drops the bprm flag that
was being used internally by AppArmor, and drops the bprm_secureexec hook.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Acked-by: Serge Hallyn <serge@hallyn.com>

security/apparmor/include/domain.h

@@ -30,7 +30,6 @@ struct aa_domain {
 #define AA_CHANGE_STACK 8
 
 int apparmor_bprm_set_creds(struct linux_binprm *bprm);
-int apparmor_bprm_secureexec(struct linux_binprm *bprm);
 
 void aa_free_domain_entries(struct aa_domain *domain);
 int aa_change_hat(const char *hats[], int count, u64 token, int flags);

security/apparmor/include/file.h

@@ -101,9 +101,6 @@ static inline struct aa_label *aa_get_file_label(struct aa_file_ctx *ctx)
 #define AA_X_INHERIT		0x4000
 #define AA_X_UNCONFINED		0x8000
 
-/* AA_SECURE_X_NEEDED - is passed in the bprm->unsafe field */
-#define AA_SECURE_X_NEEDED	0x8000
-
 /* need to make conditional which ones are being set */
 struct path_cond {
 	kuid_t uid;