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>

4 files changed, 48 insertions, 31 deletions

diff --git a/security/keys/internal.h b/security/keys/internal.h
index 9fb679c66b8a..a7252e7b2e05 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -124,8 +124,11 @@ extern struct key *request_key_and_link(struct key_type *type,
                                         struct key *dest_keyring,
                                         unsigned long flags);
 
-extern key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
+extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
                                  key_perm_t perm);
+#define KEY_LOOKUP_CREATE       0x01
+#define KEY_LOOKUP_PARTIAL      0x02
+#define KEY_LOOKUP_FOR_UNLINK   0x04
 
 extern long join_session_keyring(const char *name);
 
diff --git a/security/keys/key.c b/security/keys/key.c
index 4a1297d1ada4..3762d5b1ce64 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -642,10 +642,8 @@ struct key *key_lookup(key_serial_t id)
         goto error;
 
  found:
-        /* pretend it doesn't exist if it's dead */
-        if (atomic_read(&key->usage) == 0 ||
-            test_bit(KEY_FLAG_DEAD, &key->flags) ||
-            key->type == &key_type_dead)
+        /* pretend it doesn't exist if it is awaiting deletion */
+        if (atomic_read(&key->usage) == 0)
                 goto not_found;
 
         /* this races with key_put(), but that doesn't matter since key_put()
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 7f09fb897d2b..b85ace218395 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -103,7 +103,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
         }
 
         /* find the target keyring (which must be writable) */
-        keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+        keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
         if (IS_ERR(keyring_ref)) {
                 ret = PTR_ERR(keyring_ref);
                 goto error3;
@@ -185,7 +185,8 @@ SYSCALL_DEFINE4(request_key, const char __user *, _type,
         /* get the destination keyring if specified */
         dest_ref = NULL;
         if (destringid) {
-                dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
+                dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
+                                           KEY_WRITE);
                 if (IS_ERR(dest_ref)) {
                         ret = PTR_ERR(dest_ref);
                         goto error3;
@@ -233,9 +234,11 @@ SYSCALL_DEFINE4(request_key, const char __user *, _type,
 long keyctl_get_keyring_ID(key_serial_t id, int create)
 {
         key_ref_t key_ref;
+        unsigned long lflags;
         long ret;
 
-        key_ref = lookup_user_key(id, create, 0, KEY_SEARCH);
+        lflags = create ? KEY_LOOKUP_CREATE : 0;
+        key_ref = lookup_user_key(id, lflags, KEY_SEARCH);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error;
@@ -309,7 +312,7 @@ long keyctl_update_key(key_serial_t id,
         }
 
         /* find the target key (which must be writable) */
-        key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
+        key_ref = lookup_user_key(id, 0, KEY_WRITE);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error2;
@@ -337,7 +340,7 @@ long keyctl_revoke_key(key_serial_t id)
         key_ref_t key_ref;
         long ret;
 
-        key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
+        key_ref = lookup_user_key(id, 0, KEY_WRITE);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error;
@@ -363,7 +366,7 @@ long keyctl_keyring_clear(key_serial_t ringid)
         key_ref_t keyring_ref;
         long ret;
 
-        keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+        keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
         if (IS_ERR(keyring_ref)) {
                 ret = PTR_ERR(keyring_ref);
                 goto error;
@@ -389,13 +392,13 @@ long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
         key_ref_t keyring_ref, key_ref;
         long ret;
 
-        keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+        keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
         if (IS_ERR(keyring_ref)) {
                 ret = PTR_ERR(keyring_ref);
                 goto error;
         }
 
-        key_ref = lookup_user_key(id, 1, 0, KEY_LINK);
+        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_LINK);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error2;
@@ -423,13 +426,13 @@ long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
         key_ref_t keyring_ref, key_ref;
         long ret;
 
-        keyring_ref = lookup_user_key(ringid, 0, 0, KEY_WRITE);
+        keyring_ref = lookup_user_key(ringid, 0, KEY_WRITE);
         if (IS_ERR(keyring_ref)) {
                 ret = PTR_ERR(keyring_ref);
                 goto error;
         }
 
-        key_ref = lookup_user_key(id, 0, 0, 0);
+        key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error2;
@@ -465,7 +468,7 @@ long keyctl_describe_key(key_serial_t keyid,
         char *tmpbuf;
         long ret;
 
-        key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
+        key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
         if (IS_ERR(key_ref)) {
                 /* viewing a key under construction is permitted if we have the
                  * authorisation token handy */
@@ -474,7 +477,8 @@ long keyctl_describe_key(key_serial_t keyid,
                         if (!IS_ERR(instkey)) {
                                 key_put(instkey);
                                 key_ref = lookup_user_key(keyid,
-                                                          0, 1, 0);
+                                                          KEY_LOOKUP_PARTIAL,
+                                                          0);
                                 if (!IS_ERR(key_ref))
                                         goto okay;
                         }
@@ -558,7 +562,7 @@ long keyctl_keyring_search(key_serial_t ringid,
         }
 
         /* get the keyring at which to begin the search */
-        keyring_ref = lookup_user_key(ringid, 0, 0, KEY_SEARCH);
+        keyring_ref = lookup_user_key(ringid, 0, KEY_SEARCH);
         if (IS_ERR(keyring_ref)) {
                 ret = PTR_ERR(keyring_ref);
                 goto error2;
@@ -567,7 +571,8 @@ long keyctl_keyring_search(key_serial_t ringid,
         /* get the destination keyring if specified */
         dest_ref = NULL;
         if (destringid) {
-                dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
+                dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
+                                           KEY_WRITE);
                 if (IS_ERR(dest_ref)) {
                         ret = PTR_ERR(dest_ref);
                         goto error3;
@@ -637,7 +642,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
         long ret;
 
         /* find the key first */
-        key_ref = lookup_user_key(keyid, 0, 0, 0);
+        key_ref = lookup_user_key(keyid, 0, 0);
         if (IS_ERR(key_ref)) {
                 ret = -ENOKEY;
                 goto error;
@@ -700,7 +705,8 @@ long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
         if (uid == (uid_t) -1 && gid == (gid_t) -1)
                 goto error;
 
-        key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
+        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
+                                  KEY_SETATTR);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error;
@@ -805,7 +811,8 @@ long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
         if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
                 goto error;
 
-        key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
+        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
+                                  KEY_SETATTR);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error;
@@ -847,7 +854,7 @@ static long get_instantiation_keyring(key_serial_t ringid,
 
         /* if a specific keyring is nominated by ID, then use that */
         if (ringid > 0) {
-                dkref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
+                dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
                 if (IS_ERR(dkref))
                         return PTR_ERR(dkref);
                 *_dest_keyring = key_ref_to_ptr(dkref);
@@ -1083,7 +1090,8 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout)
         time_t expiry;
         long ret;
 
-        key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
+        key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
+                                  KEY_SETATTR);
         if (IS_ERR(key_ref)) {
                 ret = PTR_ERR(key_ref);
                 goto error;
@@ -1170,7 +1178,7 @@ long keyctl_get_security(key_serial_t keyid,
         char *context;
         long ret;
 
-        key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
+        key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
         if (IS_ERR(key_ref)) {
                 if (PTR_ERR(key_ref) != -EACCES)
                         return PTR_ERR(key_ref);
@@ -1182,7 +1190,7 @@ long keyctl_get_security(key_serial_t keyid,
                         return PTR_ERR(key_ref);
                 key_put(instkey);
 
-                key_ref = lookup_user_key(keyid, 0, 1, 0);
+                key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);
                 if (IS_ERR(key_ref))
                         return PTR_ERR(key_ref);
         }
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 */