Merge tag 'keys-namespace-20190627' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull keyring namespacing from David Howells:
 "These patches help make keys and keyrings more namespace aware.

  Firstly some miscellaneous patches to make the process easier:

   - Simplify key index_key handling so that the word-sized chunks
     assoc_array requires don't have to be shifted about, making it
     easier to add more bits into the key.

   - Cache the hash value in the key so that we don't have to calculate
     on every key we examine during a search (it involves a bunch of
     multiplications).

   - Allow keying_search() to search non-recursively.

  Then the main patches:

   - Make it so that keyring names are per-user_namespace from the point
     of view of KEYCTL_JOIN_SESSION_KEYRING so that they're not
     accessible cross-user_namespace.

     keyctl_capabilities() shows KEYCTL_CAPS1_NS_KEYRING_NAME for this.

   - Move the user and user-session keyrings to the user_namespace
     rather than the user_struct. This prevents them propagating
     directly across user_namespaces boundaries (ie. the KEY_SPEC_*
     flags will only pick from the current user_namespace).

   - Make it possible to include the target namespace in which the key
     shall operate in the index_key. This will allow the possibility of
     multiple keys with the same description, but different target
     domains to be held in the same keyring.

     keyctl_capabilities() shows KEYCTL_CAPS1_NS_KEY_TAG for this.

   - Make it so that keys are implicitly invalidated by removal of a
     domain tag, causing them to be garbage collected.

   - Institute a network namespace domain tag that allows keys to be
     differentiated by the network namespace in which they operate. New
     keys that are of a type marked 'KEY_TYPE_NET_DOMAIN' are assigned
     the network domain in force when they are created.

   - Make it so that the desired network namespace can be handed down
     into the request_key() mechanism. This allows AFS, NFS, etc. to
     request keys specific to the network namespace of the superblock.

     This also means that the keys in the DNS record cache are
     thenceforth namespaced, provided network filesystems pass the
     appropriate network namespace down into dns_query().

     For DNS, AFS and NFS are good, whilst CIFS and Ceph are not. Other
     cache keyrings, such as idmapper keyrings, also need to set the
     domain tag - for which they need access to the network namespace of
     the superblock"

* tag 'keys-namespace-20190627' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  keys: Pass the network namespace into request_key mechanism
  keys: Network namespace domain tag
  keys: Garbage collect keys for which the domain has been removed
  keys: Include target namespace in match criteria
  keys: Move the user and user-session keyrings to the user_namespace
  keys: Namespace keyring names
  keys: Add a 'recurse' flag for keyring searches
  keys: Cache the hash value to avoid lots of recalculation
  keys: Simplify key description management

1 files changed, 170 insertions, 92 deletions

diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index b99ad2c5342f..09541de31f2f 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -15,15 +15,13 @@
 #include <linux/security.h>
 #include <linux/user_namespace.h>
 #include <linux/uaccess.h>
+#include <linux/init_task.h>
 #include <keys/request_key_auth-type.h>
 #include "internal.h"
 
 /* Session keyring create vs join semaphore */
 static DEFINE_MUTEX(key_session_mutex);
 
-/* User keyring creation semaphore */
-static DEFINE_MUTEX(key_user_keyring_mutex);
-
 /* The root user's tracking struct */
 struct key_user root_key_user = {
 	.usage		= REFCOUNT_INIT(3),
@@ -35,99 +33,186 @@ struct key_user root_key_user = {
 };
 
 /*
- * Install the user and user session keyrings for the current process's UID.
+ * Get or create a user register keyring.
+ */
+static struct key *get_user_register(struct user_namespace *user_ns)
+{
+	struct key *reg_keyring = READ_ONCE(user_ns->user_keyring_register);
+
+	if (reg_keyring)
+		return reg_keyring;
+
+	down_write(&user_ns->keyring_sem);
+
+	/* Make sure there's a register keyring.  It gets owned by the
+	 * user_namespace's owner.
+	 */
+	reg_keyring = user_ns->user_keyring_register;
+	if (!reg_keyring) {
+		reg_keyring = keyring_alloc(".user_reg",
+					    user_ns->owner, INVALID_GID,
+					    &init_cred,
+					    KEY_POS_WRITE | KEY_POS_SEARCH |
+					    KEY_USR_VIEW | KEY_USR_READ,
+					    0,
+					    NULL, NULL);
+		if (!IS_ERR(reg_keyring))
+			smp_store_release(&user_ns->user_keyring_register,
+					  reg_keyring);
+	}
+
+	up_write(&user_ns->keyring_sem);
+
+	/* We don't return a ref since the keyring is pinned by the user_ns */
+	return reg_keyring;
+}
+
+/*
+ * Look up the user and user session keyrings for the current process's UID,
+ * creating them if they don't exist.
  */
-int install_user_keyrings(void)
+int look_up_user_keyrings(struct key **_user_keyring,
+			  struct key **_user_session_keyring)
 {
-	struct user_struct *user;
-	const struct cred *cred;
-	struct key *uid_keyring, *session_keyring;
+	const struct cred *cred = current_cred();
+	struct user_namespace *user_ns = current_user_ns();
+	struct key *reg_keyring, *uid_keyring, *session_keyring;
 	key_perm_t user_keyring_perm;
+	key_ref_t uid_keyring_r, session_keyring_r;
+	uid_t uid = from_kuid(user_ns, cred->user->uid);
 	char buf[20];
 	int ret;
-	uid_t uid;
 
 	user_keyring_perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL;
-	cred = current_cred();
-	user = cred->user;
-	uid = from_kuid(cred->user_ns, user->uid);
 
-	kenter("%p{%u}", user, uid);
+	kenter("%u", uid);
 
-	if (READ_ONCE(user->uid_keyring) && READ_ONCE(user->session_keyring)) {
-		kleave(" = 0 [exist]");
-		return 0;
-	}
+	reg_keyring = get_user_register(user_ns);
+	if (IS_ERR(reg_keyring))
+		return PTR_ERR(reg_keyring);
 
-	mutex_lock(&key_user_keyring_mutex);
+	down_write(&user_ns->keyring_sem);
 	ret = 0;
 
-	if (!user->uid_keyring) {
-		/* get the UID-specific keyring
-		 * - there may be one in existence already as it may have been
-		 *   pinned by a session, but the user_struct pointing to it
-		 *   may have been destroyed by setuid */
-		sprintf(buf, "_uid.%u", uid);
-
-		uid_keyring = find_keyring_by_name(buf, true);
+	/* Get the user keyring.  Note that there may be one in existence
+	 * already as it may have been pinned by a session, but the user_struct
+	 * pointing to it may have been destroyed by setuid.
+	 */
+	snprintf(buf, sizeof(buf), "_uid.%u", uid);
+	uid_keyring_r = keyring_search(make_key_ref(reg_keyring, true),
+				       &key_type_keyring, buf, false);
+	kdebug("_uid %p", uid_keyring_r);
+	if (uid_keyring_r == ERR_PTR(-EAGAIN)) {
+		uid_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID,
+					    cred, user_keyring_perm,
+					    KEY_ALLOC_UID_KEYRING |
+					    KEY_ALLOC_IN_QUOTA,
+					    NULL, reg_keyring);
 		if (IS_ERR(uid_keyring)) {
-			uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID,
-						    cred, user_keyring_perm,
-						    KEY_ALLOC_UID_KEYRING |
-							KEY_ALLOC_IN_QUOTA,
-						    NULL, NULL);
-			if (IS_ERR(uid_keyring)) {
-				ret = PTR_ERR(uid_keyring);
-				goto error;
-			}
+			ret = PTR_ERR(uid_keyring);
+			goto error;
 		}
+	} else if (IS_ERR(uid_keyring_r)) {
+		ret = PTR_ERR(uid_keyring_r);
+		goto error;
+	} else {
+		uid_keyring = key_ref_to_ptr(uid_keyring_r);
+	}
 
-		/* get a default session keyring (which might also exist
-		 * already) */
-		sprintf(buf, "_uid_ses.%u", uid);
-
-		session_keyring = find_keyring_by_name(buf, true);
+	/* Get a default session keyring (which might also exist already) */
+	snprintf(buf, sizeof(buf), "_uid_ses.%u", uid);
+	session_keyring_r = keyring_search(make_key_ref(reg_keyring, true),
+					   &key_type_keyring, buf, false);
+	kdebug("_uid_ses %p", session_keyring_r);
+	if (session_keyring_r == ERR_PTR(-EAGAIN)) {
+		session_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID,
+						cred, user_keyring_perm,
+						KEY_ALLOC_UID_KEYRING |
+						KEY_ALLOC_IN_QUOTA,
+						NULL, NULL);
 		if (IS_ERR(session_keyring)) {
-			session_keyring =
-				keyring_alloc(buf, user->uid, INVALID_GID,
-					      cred, user_keyring_perm,
-					      KEY_ALLOC_UID_KEYRING |
-						  KEY_ALLOC_IN_QUOTA,
-					      NULL, NULL);
-			if (IS_ERR(session_keyring)) {
-				ret = PTR_ERR(session_keyring);
-				goto error_release;
-			}
-
-			/* we install a link from the user session keyring to
-			 * the user keyring */
-			ret = key_link(session_keyring, uid_keyring);
-			if (ret < 0)
-				goto error_release_both;
+			ret = PTR_ERR(session_keyring);
+			goto error_release;
 		}
 
-		/* install the keyrings */
-		/* paired with READ_ONCE() */
-		smp_store_release(&user->uid_keyring, uid_keyring);
-		/* paired with READ_ONCE() */
-		smp_store_release(&user->session_keyring, session_keyring);
+		/* We install a link from the user session keyring to
+		 * the user keyring.
+		 */
+		ret = key_link(session_keyring, uid_keyring);
+		if (ret < 0)
+			goto error_release_session;
+
+		/* And only then link the user-session keyring to the
+		 * register.
+		 */
+		ret = key_link(reg_keyring, session_keyring);
+		if (ret < 0)
+			goto error_release_session;
+	} else if (IS_ERR(session_keyring_r)) {
+		ret = PTR_ERR(session_keyring_r);
+		goto error_release;
+	} else {
+		session_keyring = key_ref_to_ptr(session_keyring_r);
 	}
 
-	mutex_unlock(&key_user_keyring_mutex);
+	up_write(&user_ns->keyring_sem);
+
+	if (_user_session_keyring)
+		*_user_session_keyring = session_keyring;
+	else
+		key_put(session_keyring);
+	if (_user_keyring)
+		*_user_keyring = uid_keyring;
+	else
+		key_put(uid_keyring);
 	kleave(" = 0");
 	return 0;
 
-error_release_both:
+error_release_session:
 	key_put(session_keyring);
 error_release:
 	key_put(uid_keyring);
 error:
-	mutex_unlock(&key_user_keyring_mutex);
+	up_write(&user_ns->keyring_sem);
 	kleave(" = %d", ret);
 	return ret;
 }
 
 /*
+ * Get the user session keyring if it exists, but don't create it if it
+ * doesn't.
+ */
+struct key *get_user_session_keyring_rcu(const struct cred *cred)
+{
+	struct key *reg_keyring = READ_ONCE(cred->user_ns->user_keyring_register);
+	key_ref_t session_keyring_r;
+	char buf[20];
+
+	struct keyring_search_context ctx = {
+		.index_key.type		= &key_type_keyring,
+		.index_key.description	= buf,
+		.cred			= cred,
+		.match_data.cmp		= key_default_cmp,
+		.match_data.raw_data	= buf,
+		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
+		.flags			= KEYRING_SEARCH_DO_STATE_CHECK,
+	};
+
+	if (!reg_keyring)
+		return NULL;
+
+	ctx.index_key.desc_len = snprintf(buf, sizeof(buf), "_uid_ses.%u",
+					  from_kuid(cred->user_ns,
+						    cred->user->uid));
+
+	session_keyring_r = keyring_search_rcu(make_key_ref(reg_keyring, true),
+					       &ctx);
+	if (IS_ERR(session_keyring_r))
+		return NULL;
+	return key_ref_to_ptr(session_keyring_r);
+}
+
+/*
  * Install a thread keyring to the given credentials struct if it didn't have
  * one already.  This is allowed to overrun the quota.
  *
@@ -336,6 +421,7 @@ void key_fsgid_changed(struct cred *new_cred)
  */
 key_ref_t search_cred_keyrings_rcu(struct keyring_search_context *ctx)
 {
+	struct key *user_session;
 	key_ref_t key_ref, ret, err;
 	const struct cred *cred = ctx->cred;
 
@@ -411,10 +497,11 @@ key_ref_t search_cred_keyrings_rcu(struct keyring_search_context *ctx)
 		}
 	}
 	/* or search the user-session keyring */
-	else if (READ_ONCE(cred->user->session_keyring)) {
-		key_ref = keyring_search_rcu(
-			make_key_ref(READ_ONCE(cred->user->session_keyring), 1),
-			ctx);
+	else if ((user_session = get_user_session_keyring_rcu(cred))) {
+		key_ref = keyring_search_rcu(make_key_ref(user_session, 1),
+					     ctx);
+		key_put(user_session);
+
 		if (!IS_ERR(key_ref))
 			goto found;
 
@@ -527,10 +614,11 @@ key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
 	struct keyring_search_context ctx = {
 		.match_data.cmp		= lookup_user_key_possessed,
 		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
-		.flags			= KEYRING_SEARCH_NO_STATE_CHECK,
+		.flags			= (KEYRING_SEARCH_NO_STATE_CHECK |
+					   KEYRING_SEARCH_RECURSE),
 	};
 	struct request_key_auth *rka;
-	struct key *key;
+	struct key *key, *user_session;
 	key_ref_t key_ref, skey_ref;
 	int ret;
 
@@ -579,20 +667,20 @@ try_again:
 		if (!ctx.cred->session_keyring) {
 			/* always install a session keyring upon access if one
 			 * doesn't exist yet */
-			ret = install_user_keyrings();
+			ret = look_up_user_keyrings(NULL, &user_session);
 			if (ret < 0)
 				goto error;
 			if (lflags & KEY_LOOKUP_CREATE)
 				ret = join_session_keyring(NULL);
 			else
-				ret = install_session_keyring(
-					ctx.cred->user->session_keyring);
+				ret = install_session_keyring(user_session);
 
+			key_put(user_session);
 			if (ret < 0)
 				goto error;
 			goto reget_creds;
-		} else if (ctx.cred->session_keyring ==
-			   READ_ONCE(ctx.cred->user->session_keyring) &&
+		} else if (test_bit(KEY_FLAG_UID_KEYRING,
+				    &ctx.cred->session_keyring->flags) &&
 			   lflags & KEY_LOOKUP_CREATE) {
 			ret = join_session_keyring(NULL);
 			if (ret < 0)
@@ -606,26 +694,16 @@ try_again:
 		break;
 
 	case KEY_SPEC_USER_KEYRING:
-		if (!READ_ONCE(ctx.cred->user->uid_keyring)) {
-			ret = install_user_keyrings();
-			if (ret < 0)
-				goto error;
-		}
-
-		key = ctx.cred->user->uid_keyring;
-		__key_get(key);
+		ret = look_up_user_keyrings(&key, NULL);
+		if (ret < 0)
+			goto error;
 		key_ref = make_key_ref(key, 1);
 		break;
 
 	case KEY_SPEC_USER_SESSION_KEYRING:
-		if (!READ_ONCE(ctx.cred->user->session_keyring)) {
-			ret = install_user_keyrings();
-			if (ret < 0)
-				goto error;
-		}
-
-		key = ctx.cred->user->session_keyring;
-		__key_get(key);
+		ret = look_up_user_keyrings(NULL, &key);
+		if (ret < 0)
+			goto error;
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -874,7 +952,7 @@ void key_change_session_keyring(struct callback_head *twork)
  */
 static int __init init_root_keyring(void)
 {
-	return install_user_keyrings();
+	return look_up_user_keyrings(NULL, NULL);
 }
 
 late_initcall(init_root_keyring);