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 9fb679c..a7252e7 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 4a1297d..3762d5b 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 7f09fb8..b85ace2 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 ed929af..4739cfb 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 */