Re: [PATCH v2 2/8] exec: Factor security_bprm_creds_for_exec out of security_bprm_set_creds
From: Kees Cook <hidden>
Date: 2020-05-19 18:10:19
Also in:
linux-fsdevel, lkml
On Mon, May 18, 2020 at 07:30:10PM -0500, Eric W. Biederman wrote:
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.
Yup, awesome. One nit below. Reviewed-by: Kees Cook <redacted>
quoted hunk ↗ jump to hunk
[...]diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 0b4e32161b77..718345dd76bb 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c[...]@@ -2297,8 +2297,6 @@ static int selinux_bprm_set_creds(struct linux_binprm *bprm) /* SELinux context only depends on initial program or script and not * the script interpreter */ - if (bprm->called_set_creds) - return 0; old_tsec = selinux_cred(current_cred()); new_tsec = selinux_cred(bprm->cred);
As you've done in the other LSMs, I think this comment can be removed (or moved to the top of the function) too. -- Kees Cook