[PATCH 5/6] selinux: Use security_capable_lsm() for CAP_MAC_ADMIN checks

["Mickaël Salaün" <mic@digikod.net>]

has_cap_mac_admin() checks CAP_MAC_ADMIN with cap_capable() and then
with SELinux's own check, so that other stacked LSMs do not have to
authorize it (see commit db59000ab760 ("selinux: only invoke
capabilities and selinux for CAP_MAC_ADMIN checks")).  This also lets a
process in a Landlock domain that denies CAP_MAC_ADMIN get or set
security contexts unknown to the loaded policy.

Switch this check to security_capable_lsm(), as for AppArmor and Smack
in the previous commits.  The cred_has_capability() check is kept.

Cc: Günther Noack <gnoack@google.com>
Cc: Ondrej Mosnáček <omosnacek@gmail.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Fixes: 97c8386f1d74 ("landlock: Enforce capability restrictions")
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---
 security/selinux/hooks.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9950f89dfaa2..5d85bc06f4c5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3363,7 +3363,8 @@ static bool has_cap_mac_admin(bool audit)
 	const struct cred *cred = current_cred();
 	unsigned int opts = audit ? CAP_OPT_NONE : CAP_OPT_NOAUDIT;
 
-	if (cap_capable(cred, &init_user_ns, CAP_MAC_ADMIN, opts))
+	if (security_capable_lsm(cred, &init_user_ns, CAP_MAC_ADMIN, opts,
+				 LSM_ID_SELINUX))
 		return false;
 	if (cred_has_capability(cred, CAP_MAC_ADMIN, opts, true))
 		return false;
-- 
2.56.0