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-rw-r--r--security/keys/request_key.c821
1 files changed, 821 insertions, 0 deletions
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
new file mode 100644
index 000000000..a7673ad86
--- /dev/null
+++ b/security/keys/request_key.c
@@ -0,0 +1,821 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Request a key from userspace
+ *
+ * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * See Documentation/security/keys/request-key.rst
+ */
+
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/kmod.h>
+#include <linux/err.h>
+#include <linux/keyctl.h>
+#include <linux/slab.h>
+#include <net/net_namespace.h>
+#include "internal.h"
+#include <keys/request_key_auth-type.h>
+
+#define key_negative_timeout 60 /* default timeout on a negative key's existence */
+
+static struct key *check_cached_key(struct keyring_search_context *ctx)
+{
+#ifdef CONFIG_KEYS_REQUEST_CACHE
+ struct key *key = current->cached_requested_key;
+
+ if (key &&
+ ctx->match_data.cmp(key, &ctx->match_data) &&
+ !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
+ (1 << KEY_FLAG_REVOKED))))
+ return key_get(key);
+#endif
+ return NULL;
+}
+
+static void cache_requested_key(struct key *key)
+{
+#ifdef CONFIG_KEYS_REQUEST_CACHE
+ struct task_struct *t = current;
+
+ /* Do not cache key if it is a kernel thread */
+ if (!(t->flags & PF_KTHREAD)) {
+ key_put(t->cached_requested_key);
+ t->cached_requested_key = key_get(key);
+ set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
+ }
+#endif
+}
+
+/**
+ * complete_request_key - Complete the construction of a key.
+ * @authkey: The authorisation key.
+ * @error: The success or failute of the construction.
+ *
+ * Complete the attempt to construct a key. The key will be negated
+ * if an error is indicated. The authorisation key will be revoked
+ * unconditionally.
+ */
+void complete_request_key(struct key *authkey, int error)
+{
+ struct request_key_auth *rka = get_request_key_auth(authkey);
+ struct key *key = rka->target_key;
+
+ kenter("%d{%d},%d", authkey->serial, key->serial, error);
+
+ if (error < 0)
+ key_negate_and_link(key, key_negative_timeout, NULL, authkey);
+ else
+ key_revoke(authkey);
+}
+EXPORT_SYMBOL(complete_request_key);
+
+/*
+ * Initialise a usermode helper that is going to have a specific session
+ * keyring.
+ *
+ * This is called in context of freshly forked kthread before kernel_execve(),
+ * so we can simply install the desired session_keyring at this point.
+ */
+static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
+{
+ struct key *keyring = info->data;
+
+ return install_session_keyring_to_cred(cred, keyring);
+}
+
+/*
+ * Clean up a usermode helper with session keyring.
+ */
+static void umh_keys_cleanup(struct subprocess_info *info)
+{
+ struct key *keyring = info->data;
+ key_put(keyring);
+}
+
+/*
+ * Call a usermode helper with a specific session keyring.
+ */
+static int call_usermodehelper_keys(const char *path, char **argv, char **envp,
+ struct key *session_keyring, int wait)
+{
+ struct subprocess_info *info;
+
+ info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
+ umh_keys_init, umh_keys_cleanup,
+ session_keyring);
+ if (!info)
+ return -ENOMEM;
+
+ key_get(session_keyring);
+ return call_usermodehelper_exec(info, wait);
+}
+
+/*
+ * Request userspace finish the construction of a key
+ * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
+ */
+static int call_sbin_request_key(struct key *authkey, void *aux)
+{
+ static char const request_key[] = "/sbin/request-key";
+ struct request_key_auth *rka = get_request_key_auth(authkey);
+ const struct cred *cred = current_cred();
+ key_serial_t prkey, sskey;
+ struct key *key = rka->target_key, *keyring, *session, *user_session;
+ char *argv[9], *envp[3], uid_str[12], gid_str[12];
+ char key_str[12], keyring_str[3][12];
+ char desc[20];
+ int ret, i;
+
+ kenter("{%d},{%d},%s", key->serial, authkey->serial, rka->op);
+
+ ret = look_up_user_keyrings(NULL, &user_session);
+ if (ret < 0)
+ goto error_us;
+
+ /* allocate a new session keyring */
+ sprintf(desc, "_req.%u", key->serial);
+
+ cred = get_current_cred();
+ keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
+ KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
+ KEY_ALLOC_QUOTA_OVERRUN, NULL, NULL);
+ put_cred(cred);
+ if (IS_ERR(keyring)) {
+ ret = PTR_ERR(keyring);
+ goto error_alloc;
+ }
+
+ /* attach the auth key to the session keyring */
+ ret = key_link(keyring, authkey);
+ if (ret < 0)
+ goto error_link;
+
+ /* record the UID and GID */
+ sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid));
+ sprintf(gid_str, "%d", from_kgid(&init_user_ns, cred->fsgid));
+
+ /* we say which key is under construction */
+ sprintf(key_str, "%d", key->serial);
+
+ /* we specify the process's default keyrings */
+ sprintf(keyring_str[0], "%d",
+ cred->thread_keyring ? cred->thread_keyring->serial : 0);
+
+ prkey = 0;
+ if (cred->process_keyring)
+ prkey = cred->process_keyring->serial;
+ sprintf(keyring_str[1], "%d", prkey);
+
+ session = cred->session_keyring;
+ if (!session)
+ session = user_session;
+ sskey = session->serial;
+
+ sprintf(keyring_str[2], "%d", sskey);
+
+ /* set up a minimal environment */
+ i = 0;
+ envp[i++] = "HOME=/";
+ envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+ envp[i] = NULL;
+
+ /* set up the argument list */
+ i = 0;
+ argv[i++] = (char *)request_key;
+ argv[i++] = (char *)rka->op;
+ argv[i++] = key_str;
+ argv[i++] = uid_str;
+ argv[i++] = gid_str;
+ argv[i++] = keyring_str[0];
+ argv[i++] = keyring_str[1];
+ argv[i++] = keyring_str[2];
+ argv[i] = NULL;
+
+ /* do it */
+ ret = call_usermodehelper_keys(request_key, argv, envp, keyring,
+ UMH_WAIT_PROC);
+ kdebug("usermode -> 0x%x", ret);
+ if (ret >= 0) {
+ /* ret is the exit/wait code */
+ if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
+ key_validate(key) < 0)
+ ret = -ENOKEY;
+ else
+ /* ignore any errors from userspace if the key was
+ * instantiated */
+ ret = 0;
+ }
+
+error_link:
+ key_put(keyring);
+
+error_alloc:
+ key_put(user_session);
+error_us:
+ complete_request_key(authkey, ret);
+ kleave(" = %d", ret);
+ return ret;
+}
+
+/*
+ * Call out to userspace for key construction.
+ *
+ * Program failure is ignored in favour of key status.
+ */
+static int construct_key(struct key *key, const void *callout_info,
+ size_t callout_len, void *aux,
+ struct key *dest_keyring)
+{
+ request_key_actor_t actor;
+ struct key *authkey;
+ int ret;
+
+ kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
+
+ /* allocate an authorisation key */
+ authkey = request_key_auth_new(key, "create", callout_info, callout_len,
+ dest_keyring);
+ if (IS_ERR(authkey))
+ return PTR_ERR(authkey);
+
+ /* Make the call */
+ actor = call_sbin_request_key;
+ if (key->type->request_key)
+ actor = key->type->request_key;
+
+ ret = actor(authkey, aux);
+
+ /* check that the actor called complete_request_key() prior to
+ * returning an error */
+ WARN_ON(ret < 0 &&
+ !test_bit(KEY_FLAG_INVALIDATED, &authkey->flags));
+
+ key_put(authkey);
+ kleave(" = %d", ret);
+ return ret;
+}
+
+/*
+ * Get the appropriate destination keyring for the request.
+ *
+ * The keyring selected is returned with an extra reference upon it which the
+ * caller must release.
+ */
+static int construct_get_dest_keyring(struct key **_dest_keyring)
+{
+ struct request_key_auth *rka;
+ const struct cred *cred = current_cred();
+ struct key *dest_keyring = *_dest_keyring, *authkey;
+ int ret;
+
+ kenter("%p", dest_keyring);
+
+ /* find the appropriate keyring */
+ if (dest_keyring) {
+ /* the caller supplied one */
+ key_get(dest_keyring);
+ } else {
+ bool do_perm_check = true;
+
+ /* use a default keyring; falling through the cases until we
+ * find one that we actually have */
+ switch (cred->jit_keyring) {
+ case KEY_REQKEY_DEFL_DEFAULT:
+ case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
+ if (cred->request_key_auth) {
+ authkey = cred->request_key_auth;
+ down_read(&authkey->sem);
+ rka = get_request_key_auth(authkey);
+ if (!test_bit(KEY_FLAG_REVOKED,
+ &authkey->flags))
+ dest_keyring =
+ key_get(rka->dest_keyring);
+ up_read(&authkey->sem);
+ if (dest_keyring) {
+ do_perm_check = false;
+ break;
+ }
+ }
+
+ fallthrough;
+ case KEY_REQKEY_DEFL_THREAD_KEYRING:
+ dest_keyring = key_get(cred->thread_keyring);
+ if (dest_keyring)
+ break;
+
+ fallthrough;
+ case KEY_REQKEY_DEFL_PROCESS_KEYRING:
+ dest_keyring = key_get(cred->process_keyring);
+ if (dest_keyring)
+ break;
+
+ fallthrough;
+ case KEY_REQKEY_DEFL_SESSION_KEYRING:
+ dest_keyring = key_get(cred->session_keyring);
+
+ if (dest_keyring)
+ break;
+
+ fallthrough;
+ case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
+ ret = look_up_user_keyrings(NULL, &dest_keyring);
+ if (ret < 0)
+ return ret;
+ break;
+
+ case KEY_REQKEY_DEFL_USER_KEYRING:
+ ret = look_up_user_keyrings(&dest_keyring, NULL);
+ if (ret < 0)
+ return ret;
+ break;
+
+ case KEY_REQKEY_DEFL_GROUP_KEYRING:
+ default:
+ BUG();
+ }
+
+ /*
+ * Require Write permission on the keyring. This is essential
+ * because the default keyring may be the session keyring, and
+ * joining a keyring only requires Search permission.
+ *
+ * However, this check is skipped for the "requestor keyring" so
+ * that /sbin/request-key can itself use request_key() to add
+ * keys to the original requestor's destination keyring.
+ */
+ if (dest_keyring && do_perm_check) {
+ ret = key_permission(make_key_ref(dest_keyring, 1),
+ KEY_NEED_WRITE);
+ if (ret) {
+ key_put(dest_keyring);
+ return ret;
+ }
+ }
+ }
+
+ *_dest_keyring = dest_keyring;
+ kleave(" [dk %d]", key_serial(dest_keyring));
+ return 0;
+}
+
+/*
+ * Allocate a new key in under-construction state and attempt to link it in to
+ * the requested keyring.
+ *
+ * May return a key that's already under construction instead if there was a
+ * race between two thread calling request_key().
+ */
+static int construct_alloc_key(struct keyring_search_context *ctx,
+ struct key *dest_keyring,
+ unsigned long flags,
+ struct key_user *user,
+ struct key **_key)
+{
+ struct assoc_array_edit *edit = NULL;
+ struct key *key;
+ key_perm_t perm;
+ key_ref_t key_ref;
+ int ret;
+
+ kenter("%s,%s,,,",
+ ctx->index_key.type->name, ctx->index_key.description);
+
+ *_key = NULL;
+ mutex_lock(&user->cons_lock);
+
+ perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
+ perm |= KEY_USR_VIEW;
+ if (ctx->index_key.type->read)
+ perm |= KEY_POS_READ;
+ if (ctx->index_key.type == &key_type_keyring ||
+ ctx->index_key.type->update)
+ perm |= KEY_POS_WRITE;
+
+ key = key_alloc(ctx->index_key.type, ctx->index_key.description,
+ ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
+ perm, flags, NULL);
+ if (IS_ERR(key))
+ goto alloc_failed;
+
+ set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
+
+ if (dest_keyring) {
+ ret = __key_link_lock(dest_keyring, &key->index_key);
+ if (ret < 0)
+ goto link_lock_failed;
+ }
+
+ /*
+ * Attach the key to the destination keyring under lock, but we do need
+ * to do another check just in case someone beat us to it whilst we
+ * waited for locks.
+ *
+ * The caller might specify a comparison function which looks for keys
+ * that do not exactly match but are still equivalent from the caller's
+ * perspective. The __key_link_begin() operation must be done only after
+ * an actual key is determined.
+ */
+ mutex_lock(&key_construction_mutex);
+
+ rcu_read_lock();
+ key_ref = search_process_keyrings_rcu(ctx);
+ rcu_read_unlock();
+ if (!IS_ERR(key_ref))
+ goto key_already_present;
+
+ if (dest_keyring) {
+ ret = __key_link_begin(dest_keyring, &key->index_key, &edit);
+ if (ret < 0)
+ goto link_alloc_failed;
+ __key_link(dest_keyring, key, &edit);
+ }
+
+ mutex_unlock(&key_construction_mutex);
+ if (dest_keyring)
+ __key_link_end(dest_keyring, &key->index_key, edit);
+ mutex_unlock(&user->cons_lock);
+ *_key = key;
+ kleave(" = 0 [%d]", key_serial(key));
+ return 0;
+
+ /* the key is now present - we tell the caller that we found it by
+ * returning -EINPROGRESS */
+key_already_present:
+ key_put(key);
+ mutex_unlock(&key_construction_mutex);
+ key = key_ref_to_ptr(key_ref);
+ if (dest_keyring) {
+ ret = __key_link_begin(dest_keyring, &key->index_key, &edit);
+ if (ret < 0)
+ goto link_alloc_failed_unlocked;
+ ret = __key_link_check_live_key(dest_keyring, key);
+ if (ret == 0)
+ __key_link(dest_keyring, key, &edit);
+ __key_link_end(dest_keyring, &key->index_key, edit);
+ if (ret < 0)
+ goto link_check_failed;
+ }
+ mutex_unlock(&user->cons_lock);
+ *_key = key;
+ kleave(" = -EINPROGRESS [%d]", key_serial(key));
+ return -EINPROGRESS;
+
+link_check_failed:
+ mutex_unlock(&user->cons_lock);
+ key_put(key);
+ kleave(" = %d [linkcheck]", ret);
+ return ret;
+
+link_alloc_failed:
+ mutex_unlock(&key_construction_mutex);
+link_alloc_failed_unlocked:
+ __key_link_end(dest_keyring, &key->index_key, edit);
+link_lock_failed:
+ mutex_unlock(&user->cons_lock);
+ key_put(key);
+ kleave(" = %d [prelink]", ret);
+ return ret;
+
+alloc_failed:
+ mutex_unlock(&user->cons_lock);
+ kleave(" = %ld", PTR_ERR(key));
+ return PTR_ERR(key);
+}
+
+/*
+ * Commence key construction.
+ */
+static struct key *construct_key_and_link(struct keyring_search_context *ctx,
+ const char *callout_info,
+ size_t callout_len,
+ void *aux,
+ struct key *dest_keyring,
+ unsigned long flags)
+{
+ struct key_user *user;
+ struct key *key;
+ int ret;
+
+ kenter("");
+
+ if (ctx->index_key.type == &key_type_keyring)
+ return ERR_PTR(-EPERM);
+
+ ret = construct_get_dest_keyring(&dest_keyring);
+ if (ret)
+ goto error;
+
+ user = key_user_lookup(current_fsuid());
+ if (!user) {
+ ret = -ENOMEM;
+ goto error_put_dest_keyring;
+ }
+
+ ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
+ key_user_put(user);
+
+ if (ret == 0) {
+ ret = construct_key(key, callout_info, callout_len, aux,
+ dest_keyring);
+ if (ret < 0) {
+ kdebug("cons failed");
+ goto construction_failed;
+ }
+ } else if (ret == -EINPROGRESS) {
+ ret = 0;
+ } else {
+ goto error_put_dest_keyring;
+ }
+
+ key_put(dest_keyring);
+ kleave(" = key %d", key_serial(key));
+ return key;
+
+construction_failed:
+ key_negate_and_link(key, key_negative_timeout, NULL, NULL);
+ key_put(key);
+error_put_dest_keyring:
+ key_put(dest_keyring);
+error:
+ kleave(" = %d", ret);
+ return ERR_PTR(ret);
+}
+
+/**
+ * request_key_and_link - Request a key and cache it in a keyring.
+ * @type: The type of key we want.
+ * @description: The searchable description of the key.
+ * @domain_tag: The domain in which the key operates.
+ * @callout_info: The data to pass to the instantiation upcall (or NULL).
+ * @callout_len: The length of callout_info.
+ * @aux: Auxiliary data for the upcall.
+ * @dest_keyring: Where to cache the key.
+ * @flags: Flags to key_alloc().
+ *
+ * A key matching the specified criteria (type, description, domain_tag) is
+ * searched for in the process's keyrings and returned with its usage count
+ * incremented if found. Otherwise, if callout_info is not NULL, a key will be
+ * allocated and some service (probably in userspace) will be asked to
+ * instantiate it.
+ *
+ * If successfully found or created, the key will be linked to the destination
+ * keyring if one is provided.
+ *
+ * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
+ * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
+ * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
+ * if insufficient key quota was available to create a new key; or -ENOMEM if
+ * insufficient memory was available.
+ *
+ * If the returned key was created, then it may still be under construction,
+ * and wait_for_key_construction() should be used to wait for that to complete.
+ */
+struct key *request_key_and_link(struct key_type *type,
+ const char *description,
+ struct key_tag *domain_tag,
+ const void *callout_info,
+ size_t callout_len,
+ void *aux,
+ struct key *dest_keyring,
+ unsigned long flags)
+{
+ struct keyring_search_context ctx = {
+ .index_key.type = type,
+ .index_key.domain_tag = domain_tag,
+ .index_key.description = description,
+ .index_key.desc_len = strlen(description),
+ .cred = current_cred(),
+ .match_data.cmp = key_default_cmp,
+ .match_data.raw_data = description,
+ .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
+ .flags = (KEYRING_SEARCH_DO_STATE_CHECK |
+ KEYRING_SEARCH_SKIP_EXPIRED |
+ KEYRING_SEARCH_RECURSE),
+ };
+ struct key *key;
+ key_ref_t key_ref;
+ int ret;
+
+ kenter("%s,%s,%p,%zu,%p,%p,%lx",
+ ctx.index_key.type->name, ctx.index_key.description,
+ callout_info, callout_len, aux, dest_keyring, flags);
+
+ if (type->match_preparse) {
+ ret = type->match_preparse(&ctx.match_data);
+ if (ret < 0) {
+ key = ERR_PTR(ret);
+ goto error;
+ }
+ }
+
+ key = check_cached_key(&ctx);
+ if (key)
+ goto error_free;
+
+ /* search all the process keyrings for a key */
+ rcu_read_lock();
+ key_ref = search_process_keyrings_rcu(&ctx);
+ rcu_read_unlock();
+
+ if (!IS_ERR(key_ref)) {
+ if (dest_keyring) {
+ ret = key_task_permission(key_ref, current_cred(),
+ KEY_NEED_LINK);
+ if (ret < 0) {
+ key_ref_put(key_ref);
+ key = ERR_PTR(ret);
+ goto error_free;
+ }
+ }
+
+ key = key_ref_to_ptr(key_ref);
+ if (dest_keyring) {
+ ret = key_link(dest_keyring, key);
+ if (ret < 0) {
+ key_put(key);
+ key = ERR_PTR(ret);
+ goto error_free;
+ }
+ }
+
+ /* Only cache the key on immediate success */
+ cache_requested_key(key);
+ } else if (PTR_ERR(key_ref) != -EAGAIN) {
+ key = ERR_CAST(key_ref);
+ } else {
+ /* the search failed, but the keyrings were searchable, so we
+ * should consult userspace if we can */
+ key = ERR_PTR(-ENOKEY);
+ if (!callout_info)
+ goto error_free;
+
+ key = construct_key_and_link(&ctx, callout_info, callout_len,
+ aux, dest_keyring, flags);
+ }
+
+error_free:
+ if (type->match_free)
+ type->match_free(&ctx.match_data);
+error:
+ kleave(" = %p", key);
+ return key;
+}
+
+/**
+ * wait_for_key_construction - Wait for construction of a key to complete
+ * @key: The key being waited for.
+ * @intr: Whether to wait interruptibly.
+ *
+ * Wait for a key to finish being constructed.
+ *
+ * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
+ * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
+ * revoked or expired.
+ */
+int wait_for_key_construction(struct key *key, bool intr)
+{
+ int ret;
+
+ ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
+ intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
+ if (ret)
+ return -ERESTARTSYS;
+ ret = key_read_state(key);
+ if (ret < 0)
+ return ret;
+ return key_validate(key);
+}
+EXPORT_SYMBOL(wait_for_key_construction);
+
+/**
+ * request_key_tag - Request a key and wait for construction
+ * @type: Type of key.
+ * @description: The searchable description of the key.
+ * @domain_tag: The domain in which the key operates.
+ * @callout_info: The data to pass to the instantiation upcall (or NULL).
+ *
+ * As for request_key_and_link() except that it does not add the returned key
+ * to a keyring if found, new keys are always allocated in the user's quota,
+ * the callout_info must be a NUL-terminated string and no auxiliary data can
+ * be passed.
+ *
+ * Furthermore, it then works as wait_for_key_construction() to wait for the
+ * completion of keys undergoing construction with a non-interruptible wait.
+ */
+struct key *request_key_tag(struct key_type *type,
+ const char *description,
+ struct key_tag *domain_tag,
+ const char *callout_info)
+{
+ struct key *key;
+ size_t callout_len = 0;
+ int ret;
+
+ if (callout_info)
+ callout_len = strlen(callout_info);
+ key = request_key_and_link(type, description, domain_tag,
+ callout_info, callout_len,
+ NULL, NULL, KEY_ALLOC_IN_QUOTA);
+ if (!IS_ERR(key)) {
+ ret = wait_for_key_construction(key, false);
+ if (ret < 0) {
+ key_put(key);
+ return ERR_PTR(ret);
+ }
+ }
+ return key;
+}
+EXPORT_SYMBOL(request_key_tag);
+
+/**
+ * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
+ * @type: The type of key we want.
+ * @description: The searchable description of the key.
+ * @domain_tag: The domain in which the key operates.
+ * @callout_info: The data to pass to the instantiation upcall (or NULL).
+ * @callout_len: The length of callout_info.
+ * @aux: Auxiliary data for the upcall.
+ *
+ * As for request_key_and_link() except that it does not add the returned key
+ * to a keyring if found and new keys are always allocated in the user's quota.
+ *
+ * Furthermore, it then works as wait_for_key_construction() to wait for the
+ * completion of keys undergoing construction with a non-interruptible wait.
+ */
+struct key *request_key_with_auxdata(struct key_type *type,
+ const char *description,
+ struct key_tag *domain_tag,
+ const void *callout_info,
+ size_t callout_len,
+ void *aux)
+{
+ struct key *key;
+ int ret;
+
+ key = request_key_and_link(type, description, domain_tag,
+ callout_info, callout_len,
+ aux, NULL, KEY_ALLOC_IN_QUOTA);
+ if (!IS_ERR(key)) {
+ ret = wait_for_key_construction(key, false);
+ if (ret < 0) {
+ key_put(key);
+ return ERR_PTR(ret);
+ }
+ }
+ return key;
+}
+EXPORT_SYMBOL(request_key_with_auxdata);
+
+/**
+ * request_key_rcu - Request key from RCU-read-locked context
+ * @type: The type of key we want.
+ * @description: The name of the key we want.
+ * @domain_tag: The domain in which the key operates.
+ *
+ * Request a key from a context that we may not sleep in (such as RCU-mode
+ * pathwalk). Keys under construction are ignored.
+ *
+ * Return a pointer to the found key if successful, -ENOKEY if we couldn't find
+ * a key or some other error if the key found was unsuitable or inaccessible.
+ */
+struct key *request_key_rcu(struct key_type *type,
+ const char *description,
+ struct key_tag *domain_tag)
+{
+ struct keyring_search_context ctx = {
+ .index_key.type = type,
+ .index_key.domain_tag = domain_tag,
+ .index_key.description = description,
+ .index_key.desc_len = strlen(description),
+ .cred = current_cred(),
+ .match_data.cmp = key_default_cmp,
+ .match_data.raw_data = description,
+ .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
+ .flags = (KEYRING_SEARCH_DO_STATE_CHECK |
+ KEYRING_SEARCH_SKIP_EXPIRED),
+ };
+ struct key *key;
+ key_ref_t key_ref;
+
+ kenter("%s,%s", type->name, description);
+
+ key = check_cached_key(&ctx);
+ if (key)
+ return key;
+
+ /* search all the process keyrings for a key */
+ key_ref = search_process_keyrings_rcu(&ctx);
+ if (IS_ERR(key_ref)) {
+ key = ERR_CAST(key_ref);
+ if (PTR_ERR(key_ref) == -EAGAIN)
+ key = ERR_PTR(-ENOKEY);
+ } else {
+ key = key_ref_to_ptr(key_ref);
+ cache_requested_key(key);
+ }
+
+ kleave(" = %p", key);
+ return key;
+}
+EXPORT_SYMBOL(request_key_rcu);