Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 870 insertions, 0 deletions

diff --git a/kernel/security/keys/process_keys.c b/kernel/security/keys/process_keys.c
new file mode 100644
index 000000000..bd536cb22
--- /dev/null
+++ b/kernel/security/keys/process_keys.c
@@ -0,0 +1,870 @@
+/* Manage a process's keyrings
+ *
+ * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/keyctl.h>
+#include <linux/fs.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/security.h>
+#include <linux/user_namespace.h>
+#include <asm/uaccess.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		= ATOMIC_INIT(3),
+	.cons_lock	= __MUTEX_INITIALIZER(root_key_user.cons_lock),
+	.lock		= __SPIN_LOCK_UNLOCKED(root_key_user.lock),
+	.nkeys		= ATOMIC_INIT(2),
+	.nikeys		= ATOMIC_INIT(2),
+	.uid		= GLOBAL_ROOT_UID,
+};
+
+/*
+ * Install the user and user session keyrings for the current process's UID.
+ */
+int install_user_keyrings(void)
+{
+	struct user_struct *user;
+	const struct cred *cred;
+	struct key *uid_keyring, *session_keyring;
+	key_perm_t user_keyring_perm;
+	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);
+
+	if (user->uid_keyring && user->session_keyring) {
+		kleave(" = 0 [exist]");
+		return 0;
+	}
+
+	mutex_lock(&key_user_keyring_mutex);
+	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);
+		if (IS_ERR(uid_keyring)) {
+			uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID,
+						    cred, user_keyring_perm,
+						    KEY_ALLOC_IN_QUOTA, NULL);
+			if (IS_ERR(uid_keyring)) {
+				ret = PTR_ERR(uid_keyring);
+				goto error;
+			}
+		}
+
+		/* get a default session keyring (which might also exist
+		 * already) */
+		sprintf(buf, "_uid_ses.%u", uid);
+
+		session_keyring = find_keyring_by_name(buf, true);
+		if (IS_ERR(session_keyring)) {
+			session_keyring =
+				keyring_alloc(buf, user->uid, INVALID_GID,
+					      cred, user_keyring_perm,
+					      KEY_ALLOC_IN_QUOTA, 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;
+		}
+
+		/* install the keyrings */
+		user->uid_keyring = uid_keyring;
+		user->session_keyring = session_keyring;
+	}
+
+	mutex_unlock(&key_user_keyring_mutex);
+	kleave(" = 0");
+	return 0;
+
+error_release_both:
+	key_put(session_keyring);
+error_release:
+	key_put(uid_keyring);
+error:
+	mutex_unlock(&key_user_keyring_mutex);
+	kleave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * Install a fresh thread keyring directly to new credentials.  This keyring is
+ * allowed to overrun the quota.
+ */
+int install_thread_keyring_to_cred(struct cred *new)
+{
+	struct key *keyring;
+
+	keyring = keyring_alloc("_tid", new->uid, new->gid, new,
+				KEY_POS_ALL | KEY_USR_VIEW,
+				KEY_ALLOC_QUOTA_OVERRUN, NULL);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	new->thread_keyring = keyring;
+	return 0;
+}
+
+/*
+ * Install a fresh thread keyring, discarding the old one.
+ */
+static int install_thread_keyring(void)
+{
+	struct cred *new;
+	int ret;
+
+	new = prepare_creds();
+	if (!new)
+		return -ENOMEM;
+
+	BUG_ON(new->thread_keyring);
+
+	ret = install_thread_keyring_to_cred(new);
+	if (ret < 0) {
+		abort_creds(new);
+		return ret;
+	}
+
+	return commit_creds(new);
+}
+
+/*
+ * Install a process keyring directly to a credentials struct.
+ *
+ * Returns -EEXIST if there was already a process keyring, 0 if one installed,
+ * and other value on any other error
+ */
+int install_process_keyring_to_cred(struct cred *new)
+{
+	struct key *keyring;
+
+	if (new->process_keyring)
+		return -EEXIST;
+
+	keyring = keyring_alloc("_pid", new->uid, new->gid, new,
+				KEY_POS_ALL | KEY_USR_VIEW,
+				KEY_ALLOC_QUOTA_OVERRUN, NULL);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	new->process_keyring = keyring;
+	return 0;
+}
+
+/*
+ * Make sure a process keyring is installed for the current process.  The
+ * existing process keyring is not replaced.
+ *
+ * Returns 0 if there is a process keyring by the end of this function, some
+ * error otherwise.
+ */
+static int install_process_keyring(void)
+{
+	struct cred *new;
+	int ret;
+
+	new = prepare_creds();
+	if (!new)
+		return -ENOMEM;
+
+	ret = install_process_keyring_to_cred(new);
+	if (ret < 0) {
+		abort_creds(new);
+		return ret != -EEXIST ? ret : 0;
+	}
+
+	return commit_creds(new);
+}
+
+/*
+ * Install a session keyring directly to a credentials struct.
+ */
+int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
+{
+	unsigned long flags;
+	struct key *old;
+
+	might_sleep();
+
+	/* create an empty session keyring */
+	if (!keyring) {
+		flags = KEY_ALLOC_QUOTA_OVERRUN;
+		if (cred->session_keyring)
+			flags = KEY_ALLOC_IN_QUOTA;
+
+		keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
+					KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
+					flags, NULL);
+		if (IS_ERR(keyring))
+			return PTR_ERR(keyring);
+	} else {
+		__key_get(keyring);
+	}
+
+	/* install the keyring */
+	old = cred->session_keyring;
+	rcu_assign_pointer(cred->session_keyring, keyring);
+
+	if (old)
+		key_put(old);
+
+	return 0;
+}
+
+/*
+ * Install a session keyring, discarding the old one.  If a keyring is not
+ * supplied, an empty one is invented.
+ */
+static int install_session_keyring(struct key *keyring)
+{
+	struct cred *new;
+	int ret;
+
+	new = prepare_creds();
+	if (!new)
+		return -ENOMEM;
+
+	ret = install_session_keyring_to_cred(new, keyring);
+	if (ret < 0) {
+		abort_creds(new);
+		return ret;
+	}
+
+	return commit_creds(new);
+}
+
+/*
+ * Handle the fsuid changing.
+ */
+void key_fsuid_changed(struct task_struct *tsk)
+{
+	/* update the ownership of the thread keyring */
+	BUG_ON(!tsk->cred);
+	if (tsk->cred->thread_keyring) {
+		down_write(&tsk->cred->thread_keyring->sem);
+		tsk->cred->thread_keyring->uid = tsk->cred->fsuid;
+		up_write(&tsk->cred->thread_keyring->sem);
+	}
+}
+
+/*
+ * Handle the fsgid changing.
+ */
+void key_fsgid_changed(struct task_struct *tsk)
+{
+	/* update the ownership of the thread keyring */
+	BUG_ON(!tsk->cred);
+	if (tsk->cred->thread_keyring) {
+		down_write(&tsk->cred->thread_keyring->sem);
+		tsk->cred->thread_keyring->gid = tsk->cred->fsgid;
+		up_write(&tsk->cred->thread_keyring->sem);
+	}
+}
+
+/*
+ * Search the process keyrings attached to the supplied cred for the first
+ * matching key.
+ *
+ * The search criteria are the type and the match function.  The description is
+ * given to the match function as a parameter, but doesn't otherwise influence
+ * the search.  Typically the match function will compare the description
+ * parameter to the key's description.
+ *
+ * This can only search keyrings that grant Search permission to the supplied
+ * credentials.  Keyrings linked to searched keyrings will also be searched if
+ * they grant Search permission too.  Keys can only be found if they grant
+ * Search permission to the credentials.
+ *
+ * Returns a pointer to the key with the key usage count incremented if
+ * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
+ * matched negative keys.
+ *
+ * In the case of a successful return, the possession attribute is set on the
+ * returned key reference.
+ */
+key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx)
+{
+	key_ref_t key_ref, ret, err;
+
+	/* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
+	 * searchable, but we failed to find a key or we found a negative key;
+	 * otherwise we want to return a sample error (probably -EACCES) if
+	 * none of the keyrings were searchable
+	 *
+	 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
+	 */
+	key_ref = NULL;
+	ret = NULL;
+	err = ERR_PTR(-EAGAIN);
+
+	/* search the thread keyring first */
+	if (ctx->cred->thread_keyring) {
+		key_ref = keyring_search_aux(
+			make_key_ref(ctx->cred->thread_keyring, 1), ctx);
+		if (!IS_ERR(key_ref))
+			goto found;
+
+		switch (PTR_ERR(key_ref)) {
+		case -EAGAIN: /* no key */
+		case -ENOKEY: /* negative key */
+			ret = key_ref;
+			break;
+		default:
+			err = key_ref;
+			break;
+		}
+	}
+
+	/* search the process keyring second */
+	if (ctx->cred->process_keyring) {
+		key_ref = keyring_search_aux(
+			make_key_ref(ctx->cred->process_keyring, 1), ctx);
+		if (!IS_ERR(key_ref))
+			goto found;
+
+		switch (PTR_ERR(key_ref)) {
+		case -EAGAIN: /* no key */
+			if (ret)
+				break;
+		case -ENOKEY: /* negative key */
+			ret = key_ref;
+			break;
+		default:
+			err = key_ref;
+			break;
+		}
+	}
+
+	/* search the session keyring */
+	if (ctx->cred->session_keyring) {
+		rcu_read_lock();
+		key_ref = keyring_search_aux(
+			make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1),
+			ctx);
+		rcu_read_unlock();
+
+		if (!IS_ERR(key_ref))
+			goto found;
+
+		switch (PTR_ERR(key_ref)) {
+		case -EAGAIN: /* no key */
+			if (ret)
+				break;
+		case -ENOKEY: /* negative key */
+			ret = key_ref;
+			break;
+		default:
+			err = key_ref;
+			break;
+		}
+	}
+	/* or search the user-session keyring */
+	else if (ctx->cred->user->session_keyring) {
+		key_ref = keyring_search_aux(
+			make_key_ref(ctx->cred->user->session_keyring, 1),
+			ctx);
+		if (!IS_ERR(key_ref))
+			goto found;
+
+		switch (PTR_ERR(key_ref)) {
+		case -EAGAIN: /* no key */
+			if (ret)
+				break;
+		case -ENOKEY: /* negative key */
+			ret = key_ref;
+			break;
+		default:
+			err = key_ref;
+			break;
+		}
+	}
+
+	/* no key - decide on the error we're going to go for */
+	key_ref = ret ? ret : err;
+
+found:
+	return key_ref;
+}
+
+/*
+ * Search the process keyrings attached to the supplied cred for the first
+ * matching key in the manner of search_my_process_keyrings(), but also search
+ * the keys attached to the assumed authorisation key using its credentials if
+ * one is available.
+ *
+ * Return same as search_my_process_keyrings().
+ */
+key_ref_t search_process_keyrings(struct keyring_search_context *ctx)
+{
+	struct request_key_auth *rka;
+	key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
+
+	might_sleep();
+
+	key_ref = search_my_process_keyrings(ctx);
+	if (!IS_ERR(key_ref))
+		goto found;
+	err = key_ref;
+
+	/* if this process has an instantiation authorisation key, then we also
+	 * search the keyrings of the process mentioned there
+	 * - we don't permit access to request_key auth keys via this method
+	 */
+	if (ctx->cred->request_key_auth &&
+	    ctx->cred == current_cred() &&
+	    ctx->index_key.type != &key_type_request_key_auth
+	    ) {
+		const struct cred *cred = ctx->cred;
+
+		/* defend against the auth key being revoked */
+		down_read(&cred->request_key_auth->sem);
+
+		if (key_validate(ctx->cred->request_key_auth) == 0) {
+			rka = ctx->cred->request_key_auth->payload.data;
+
+			ctx->cred = rka->cred;
+			key_ref = search_process_keyrings(ctx);
+			ctx->cred = cred;
+
+			up_read(&cred->request_key_auth->sem);
+
+			if (!IS_ERR(key_ref))
+				goto found;
+
+			ret = key_ref;
+		} else {
+			up_read(&cred->request_key_auth->sem);
+		}
+	}
+
+	/* no key - decide on the error we're going to go for */
+	if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
+		key_ref = ERR_PTR(-ENOKEY);
+	else if (err == ERR_PTR(-EACCES))
+		key_ref = ret;
+	else
+		key_ref = err;
+
+found:
+	return key_ref;
+}
+
+/*
+ * See if the key we're looking at is the target key.
+ */
+bool lookup_user_key_possessed(const struct key *key,
+			       const struct key_match_data *match_data)
+{
+	return key == match_data->raw_data;
+}
+
+/*
+ * Look up a key ID given us by userspace with a given permissions mask to get
+ * the key it refers to.
+ *
+ * Flags can be passed to request that special keyrings be created if referred
+ * to directly, to permit partially constructed keys to be found and to skip
+ * validity and permission checks on the found key.
+ *
+ * Returns a pointer to the key with an incremented usage count if successful;
+ * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
+ * to a key or the best found key was a negative key; -EKEYREVOKED or
+ * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
+ * found key doesn't grant the requested permit or the LSM denied access to it;
+ * or -ENOMEM if a special keyring couldn't be created.
+ *
+ * In the case of a successful return, the possession attribute is set on the
+ * returned key reference.
+ */
+key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
+			  key_perm_t perm)
+{
+	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,
+	};
+	struct request_key_auth *rka;
+	struct key *key;
+	key_ref_t key_ref, skey_ref;
+	int ret;
+
+try_again:
+	ctx.cred = get_current_cred();
+	key_ref = ERR_PTR(-ENOKEY);
+
+	switch (id) {
+	case KEY_SPEC_THREAD_KEYRING:
+		if (!ctx.cred->thread_keyring) {
+			if (!(lflags & KEY_LOOKUP_CREATE))
+				goto error;
+
+			ret = install_thread_keyring();
+			if (ret < 0) {
+				key_ref = ERR_PTR(ret);
+				goto error;
+			}
+			goto reget_creds;
+		}
+
+		key = ctx.cred->thread_keyring;
+		__key_get(key);
+		key_ref = make_key_ref(key, 1);
+		break;
+
+	case KEY_SPEC_PROCESS_KEYRING:
+		if (!ctx.cred->process_keyring) {
+			if (!(lflags & KEY_LOOKUP_CREATE))
+				goto error;
+
+			ret = install_process_keyring();
+			if (ret < 0) {
+				key_ref = ERR_PTR(ret);
+				goto error;
+			}
+			goto reget_creds;
+		}
+
+		key = ctx.cred->process_keyring;
+		__key_get(key);
+		key_ref = make_key_ref(key, 1);
+		break;
+
+	case KEY_SPEC_SESSION_KEYRING:
+		if (!ctx.cred->session_keyring) {
+			/* always install a session keyring upon access if one
+			 * doesn't exist yet */
+			ret = install_user_keyrings();
+			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);
+
+			if (ret < 0)
+				goto error;
+			goto reget_creds;
+		} else if (ctx.cred->session_keyring ==
+			   ctx.cred->user->session_keyring &&
+			   lflags & KEY_LOOKUP_CREATE) {
+			ret = join_session_keyring(NULL);
+			if (ret < 0)
+				goto error;
+			goto reget_creds;
+		}
+
+		rcu_read_lock();
+		key = rcu_dereference(ctx.cred->session_keyring);
+		__key_get(key);
+		rcu_read_unlock();
+		key_ref = make_key_ref(key, 1);
+		break;
+
+	case KEY_SPEC_USER_KEYRING:
+		if (!ctx.cred->user->uid_keyring) {
+			ret = install_user_keyrings();
+			if (ret < 0)
+				goto error;
+		}
+
+		key = ctx.cred->user->uid_keyring;
+		__key_get(key);
+		key_ref = make_key_ref(key, 1);
+		break;
+
+	case KEY_SPEC_USER_SESSION_KEYRING:
+		if (!ctx.cred->user->session_keyring) {
+			ret = install_user_keyrings();
+			if (ret < 0)
+				goto error;
+		}
+
+		key = ctx.cred->user->session_keyring;
+		__key_get(key);
+		key_ref = make_key_ref(key, 1);
+		break;
+
+	case KEY_SPEC_GROUP_KEYRING:
+		/* group keyrings are not yet supported */
+		key_ref = ERR_PTR(-EINVAL);
+		goto error;
+
+	case KEY_SPEC_REQKEY_AUTH_KEY:
+		key = ctx.cred->request_key_auth;
+		if (!key)
+			goto error;
+
+		__key_get(key);
+		key_ref = make_key_ref(key, 1);
+		break;
+
+	case KEY_SPEC_REQUESTOR_KEYRING:
+		if (!ctx.cred->request_key_auth)
+			goto error;
+
+		down_read(&ctx.cred->request_key_auth->sem);
+		if (test_bit(KEY_FLAG_REVOKED,
+			     &ctx.cred->request_key_auth->flags)) {
+			key_ref = ERR_PTR(-EKEYREVOKED);
+			key = NULL;
+		} else {
+			rka = ctx.cred->request_key_auth->payload.data;
+			key = rka->dest_keyring;
+			__key_get(key);
+		}
+		up_read(&ctx.cred->request_key_auth->sem);
+		if (!key)
+			goto error;
+		key_ref = make_key_ref(key, 1);
+		break;
+
+	default:
+		key_ref = ERR_PTR(-EINVAL);
+		if (id < 1)
+			goto error;
+
+		key = key_lookup(id);
+		if (IS_ERR(key)) {
+			key_ref = ERR_CAST(key);
+			goto error;
+		}
+
+		key_ref = make_key_ref(key, 0);
+
+		/* check to see if we possess the key */
+		ctx.index_key.type		= key->type;
+		ctx.index_key.description	= key->description;
+		ctx.index_key.desc_len		= strlen(key->description);
+		ctx.match_data.raw_data		= key;
+		kdebug("check possessed");
+		skey_ref = search_process_keyrings(&ctx);
+		kdebug("possessed=%p", skey_ref);
+
+		if (!IS_ERR(skey_ref)) {
+			key_put(key);
+			key_ref = skey_ref;
+		}
+
+		break;
+	}
+
+	/* 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:
+			goto invalid_key;
+		default:
+			if (perm)
+				goto invalid_key;
+		case 0:
+			break;
+		}
+	} else if (perm) {
+		ret = key_validate(key);
+		if (ret < 0)
+			goto invalid_key;
+	}
+
+	ret = -EIO;
+	if (!(lflags & KEY_LOOKUP_PARTIAL) &&
+	    !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
+		goto invalid_key;
+
+	/* check the permissions */
+	ret = key_task_permission(key_ref, ctx.cred, perm);
+	if (ret < 0)
+		goto invalid_key;
+
+	key->last_used_at = current_kernel_time().tv_sec;
+
+error:
+	put_cred(ctx.cred);
+	return key_ref;
+
+invalid_key:
+	key_ref_put(key_ref);
+	key_ref = ERR_PTR(ret);
+	goto error;
+
+	/* if we attempted to install a keyring, then it may have caused new
+	 * creds to be installed */
+reget_creds:
+	put_cred(ctx.cred);
+	goto try_again;
+}
+
+/*
+ * Join the named keyring as the session keyring if possible else attempt to
+ * create a new one of that name and join that.
+ *
+ * If the name is NULL, an empty anonymous keyring will be installed as the
+ * session keyring.
+ *
+ * Named session keyrings are joined with a semaphore held to prevent the
+ * keyrings from going away whilst the attempt is made to going them and also
+ * to prevent a race in creating compatible session keyrings.
+ */
+long join_session_keyring(const char *name)
+{
+	const struct cred *old;
+	struct cred *new;
+	struct key *keyring;
+	long ret, serial;
+
+	new = prepare_creds();
+	if (!new)
+		return -ENOMEM;
+	old = current_cred();
+
+	/* if no name is provided, install an anonymous keyring */
+	if (!name) {
+		ret = install_session_keyring_to_cred(new, NULL);
+		if (ret < 0)
+			goto error;
+
+		serial = new->session_keyring->serial;
+		ret = commit_creds(new);
+		if (ret == 0)
+			ret = serial;
+		goto okay;
+	}
+
+	/* allow the user to join or create a named keyring */
+	mutex_lock(&key_session_mutex);
+
+	/* look for an existing keyring of this name */
+	keyring = find_keyring_by_name(name, false);
+	if (PTR_ERR(keyring) == -ENOKEY) {
+		/* not found - try and create a new one */
+		keyring = keyring_alloc(
+			name, old->uid, old->gid, old,
+			KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
+			KEY_ALLOC_IN_QUOTA, NULL);
+		if (IS_ERR(keyring)) {
+			ret = PTR_ERR(keyring);
+			goto error2;
+		}
+	} else if (IS_ERR(keyring)) {
+		ret = PTR_ERR(keyring);
+		goto error2;
+	} else if (keyring == new->session_keyring) {
+		ret = 0;
+		goto error2;
+	}
+
+	/* we've got a keyring - now to install it */
+	ret = install_session_keyring_to_cred(new, keyring);
+	if (ret < 0)
+		goto error2;
+
+	commit_creds(new);
+	mutex_unlock(&key_session_mutex);
+
+	ret = keyring->serial;
+	key_put(keyring);
+okay:
+	return ret;
+
+error2:
+	mutex_unlock(&key_session_mutex);
+error:
+	abort_creds(new);
+	return ret;
+}
+
+/*
+ * Replace a process's session keyring on behalf of one of its children when
+ * the target  process is about to resume userspace execution.
+ */
+void key_change_session_keyring(struct callback_head *twork)
+{
+	const struct cred *old = current_cred();
+	struct cred *new = container_of(twork, struct cred, rcu);
+
+	if (unlikely(current->flags & PF_EXITING)) {
+		put_cred(new);
+		return;
+	}
+
+	new->  uid	= old->  uid;
+	new-> euid	= old-> euid;
+	new-> suid	= old-> suid;
+	new->fsuid	= old->fsuid;
+	new->  gid	= old->  gid;
+	new-> egid	= old-> egid;
+	new-> sgid	= old-> sgid;
+	new->fsgid	= old->fsgid;
+	new->user	= get_uid(old->user);
+	new->user_ns	= get_user_ns(old->user_ns);
+	new->group_info	= get_group_info(old->group_info);
+
+	new->securebits	= old->securebits;
+	new->cap_inheritable	= old->cap_inheritable;
+	new->cap_permitted	= old->cap_permitted;
+	new->cap_effective	= old->cap_effective;
+	new->cap_bset		= old->cap_bset;
+
+	new->jit_keyring	= old->jit_keyring;
+	new->thread_keyring	= key_get(old->thread_keyring);
+	new->process_keyring	= key_get(old->process_keyring);
+
+	security_transfer_creds(new, old);
+
+	commit_creds(new);
+}
+
+/*
+ * Make sure that root's user and user-session keyrings exist.
+ */
+static int __init init_root_keyring(void)
+{
+	return install_user_keyrings();
+}
+
+late_initcall(init_root_keyring);