KEYS: Deal with dead-type keys appropriately [try #6]

Allow keys for which the key type has been removed to be unlinked.  Currently
dead-type keys can only be disposed of by completely clearing the keyrings
that point to them.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 13 insertions, 5 deletions

diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index ed929af466d3..4739cfbb41b7 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -487,7 +487,7 @@ static int lookup_user_key_possessed(const struct key *key, const void *target)
  * - don't create special keyrings unless so requested
  * - partially constructed keys aren't found unless requested
  */
-key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
+key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
                           key_perm_t perm)
 {
         struct request_key_auth *rka;
@@ -503,7 +503,7 @@ try_again:
         switch (id) {
         case KEY_SPEC_THREAD_KEYRING:
                 if (!cred->thread_keyring) {
-                        if (!create)
+                        if (!(lflags & KEY_LOOKUP_CREATE))
                                 goto error;
 
                         ret = install_thread_keyring();
@@ -521,7 +521,7 @@ try_again:
 
         case KEY_SPEC_PROCESS_KEYRING:
                 if (!cred->tgcred->process_keyring) {
-                        if (!create)
+                        if (!(lflags & KEY_LOOKUP_CREATE))
                                 goto error;
 
                         ret = install_process_keyring();
@@ -642,7 +642,14 @@ try_again:
                 break;
         }
 
-        if (!partial) {
+        /* unlink does not use the nominated key in any way, so can skip all
+         * the permission checks as it is only concerned with the keyring */
+        if (lflags & KEY_LOOKUP_FOR_UNLINK) {
+                ret = 0;
+                goto error;
+        }
+
+        if (!(lflags & KEY_LOOKUP_PARTIAL)) {
                 ret = wait_for_key_construction(key, true);
                 switch (ret) {
                 case -ERESTARTSYS:
@@ -660,7 +667,8 @@ try_again:
         }
 
         ret = -EIO;
-        if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
+        if (!(lflags & KEY_LOOKUP_PARTIAL) &&
+            !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
                 goto invalid_key;
 
         /* check the permissions */