netlabel: Replace protocol/NetLabel linking with refrerence counts

NetLabel has always had a list of backpointers in the CIPSO DOI definition
structure which pointed to the NetLabel LSM domain mapping structures which
referenced the CIPSO DOI struct.  The rationale for this was that when an
administrator removed a CIPSO DOI from the system all of the associated
NetLabel LSM domain mappings should be removed as well; a list of
backpointers made this a simple operation.

Unfortunately, while the backpointers did make the removal easier they were
a bit of a mess from an implementation point of view which was making
further development difficult.  Since the removal of a CIPSO DOI is a
realtively rare event it seems to make sense to remove this backpointer
list as the optimization was hurting us more then it was helping.  However,
we still need to be able to track when a CIPSO DOI definition is being used
so replace the backpointer list with a reference count.  In order to
preserve the current functionality of removing the associated LSM domain
mappings when a CIPSO DOI is removed we walk the LSM domain mapping table,
removing the relevant entries.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Reviewed-by: James Morris <jmorris@namei.org>

1 files changed, 6 insertions, 18 deletions

diff --git a/net/netlabel/netlabel_mgmt.c b/net/netlabel/netlabel_mgmt.c
index 44be5d5261f4..c4e18c7bc0c1 100644
--- a/net/netlabel/netlabel_mgmt.c
+++ b/net/netlabel/netlabel_mgmt.c
@@ -122,18 +122,12 @@ static int netlbl_mgmt_add(struct sk_buff *skb, struct genl_info *info)
                         goto add_failure;
 
                 tmp_val = nla_get_u32(info->attrs[NLBL_MGMT_A_CV4DOI]);
-                /* We should be holding a rcu_read_lock() here while we hold
-                 * the result but since the entry will always be deleted when
-                 * the CIPSO DOI is deleted we aren't going to keep the
-                 * lock. */
-                rcu_read_lock();
                 entry->type_def.cipsov4 = cipso_v4_doi_getdef(tmp_val);
-                if (entry->type_def.cipsov4 == NULL) {
-                        rcu_read_unlock();
+                if (entry->type_def.cipsov4 == NULL)
                         goto add_failure;
-                }
                 ret_val = netlbl_domhsh_add(entry, &audit_info);
-                rcu_read_unlock();
+                if (ret_val != 0)
+                        cipso_v4_doi_putdef(entry->type_def.cipsov4);
                 break;
         default:
                 goto add_failure;
@@ -294,18 +288,12 @@ static int netlbl_mgmt_adddef(struct sk_buff *skb, struct genl_info *info)
                         goto adddef_failure;
 
                 tmp_val = nla_get_u32(info->attrs[NLBL_MGMT_A_CV4DOI]);
-                /* We should be holding a rcu_read_lock() here while we hold
-                 * the result but since the entry will always be deleted when
-                 * the CIPSO DOI is deleted we aren't going to keep the
-                 * lock. */
-                rcu_read_lock();
                 entry->type_def.cipsov4 = cipso_v4_doi_getdef(tmp_val);
-                if (entry->type_def.cipsov4 == NULL) {
-                        rcu_read_unlock();
+                if (entry->type_def.cipsov4 == NULL)
                         goto adddef_failure;
-                }
                 ret_val = netlbl_domhsh_add_default(entry, &audit_info);
-                rcu_read_unlock();
+                if (ret_val != 0)
+                        cipso_v4_doi_putdef(entry->type_def.cipsov4);
                 break;
         default:
                 goto adddef_failure;