exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds

Today security_bprm_set_creds has several implementations:
apparmor_bprm_set_creds, cap_bprm_set_creds, selinux_bprm_set_creds,
smack_bprm_set_creds, and tomoyo_bprm_set_creds.

Except for cap_bprm_set_creds they all test bprm->called_set_creds and
return immediately if it is true.  The function cap_bprm_set_creds
ignores bprm->calld_sed_creds entirely.

Create a new LSM hook security_bprm_creds_for_exec that is called just
before prepare_binprm in __do_execve_file, resulting in a LSM hook
that is called exactly once for the entire of exec.  Modify the bits
of security_bprm_set_creds that only want to be called once per exec
into security_bprm_creds_for_exec, leaving only cap_bprm_set_creds
behind.

Remove bprm->called_set_creds all of it's former users have been moved
to security_bprm_creds_for_exec.

Add or upate comments a appropriate to bring them up to date and
to reflect this change.

Link: https://lkml.kernel.org/r/87v9kszrzh.fsf_-_@x220.int.ebiederm.org
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com> # For the LSM and Smack bits
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/security/apparmor/include/domain.h b/security/apparmor/include/domain.h
index 21b875fe2d37..d14928fe1c6f 100644
--- a/security/apparmor/include/domain.h
+++ b/security/apparmor/include/domain.h
@@ -30,7 +30,7 @@ struct aa_domain {
 struct aa_label *x_table_lookup(struct aa_profile *profile, u32 xindex,
 				const char **name);
 
-int apparmor_bprm_set_creds(struct linux_binprm *bprm);
+int apparmor_bprm_creds_for_exec(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);