selinux: move policy commit after updating selinuxfs

With the refactoring of the policy load logic in the security
server from the previous change, it is now possible to split out
the committing of the new policy from security_load_policy() and
perform it only after successful updating of selinuxfs.  Change
security_load_policy() to return the newly populated policy
data structures to the caller, export selinux_policy_commit()
for external callers, and introduce selinux_policy_cancel() to
provide a way to cancel the policy load in the event of an error
during updating of the selinuxfs directory tree.  Further, rework
the interfaces used by selinuxfs to get information from the policy
when creating the new directory tree to take and act upon the
new policy data structure rather than the current/active policy.
Update selinuxfs to use these updated and new interfaces.  While
we are here, stop re-creating the policy_capabilities directory
on each policy load since it does not depend on the policy, and
stop trying to create the booleans and classes directories during
the initial creation of selinuxfs since no information is available
until first policy load.

After this change, a failure while updating the booleans and class
directories will cause the entire policy load to be canceled, leaving
the original policy intact, and policy load notifications to userspace
will only happen after a successful completion of updating those
directories.  This does not (yet) provide full atomicity with respect
to the updating of the directory trees themselves.

Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index 02dd91c12235..c68ed2beadff 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -85,6 +85,7 @@ extern int selinux_enabled_boot;
 
 struct selinux_avc;
 struct selinux_ss;
+struct selinux_policy;
 
 struct selinux_state {
 #ifdef CONFIG_SECURITY_SELINUX_DISABLE
@@ -210,7 +211,12 @@ static inline bool selinux_policycap_genfs_seclabel_symlinks(void)
 
 int security_mls_enabled(struct selinux_state *state);
 int security_load_policy(struct selinux_state *state,
-			 void *data, size_t len);
+			void *data, size_t len,
+			struct selinux_policy **newpolicyp);
+void selinux_policy_commit(struct selinux_state *state,
+			struct selinux_policy *newpolicy);
+void selinux_policy_cancel(struct selinux_state *state,
+			struct selinux_policy *policy);
 int security_read_policy(struct selinux_state *state,
 			 void **data, size_t *len);
 size_t security_policydb_len(struct selinux_state *state);
@@ -344,9 +350,9 @@ int security_net_peersid_resolve(struct selinux_state *state,
 				 u32 xfrm_sid,
 				 u32 *peer_sid);
 
-int security_get_classes(struct selinux_state *state,
+int security_get_classes(struct selinux_policy *policy,
 			 char ***classes, int *nclasses);
-int security_get_permissions(struct selinux_state *state,
+int security_get_permissions(struct selinux_policy *policy,
 			     char *class, char ***perms, int *nperms);
 int security_get_reject_unknown(struct selinux_state *state);
 int security_get_allow_unknown(struct selinux_state *state);
@@ -366,6 +372,10 @@ int security_genfs_sid(struct selinux_state *state,
 		       const char *fstype, char *name, u16 sclass,
 		       u32 *sid);
 
+int selinux_policy_genfs_sid(struct selinux_policy *policy,
+		       const char *fstype, char *name, u16 sclass,
+		       u32 *sid);
+
 #ifdef CONFIG_NETLABEL
 int security_netlbl_secattr_to_sid(struct selinux_state *state,
 				   struct netlbl_lsm_secattr *secattr,