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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* Userspace key control operations
  *
  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */
 
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/sched/task.h>
 #include <linux/slab.h>
 #include <linux/syscalls.h>
 #include <linux/key.h>
 #include <linux/keyctl.h>
 #include <linux/fs.h>
 #include <linux/capability.h>
 #include <linux/cred.h>
 #include <linux/string.h>
 #include <linux/err.h>
 #include <linux/vmalloc.h>
 #include <linux/security.h>
 #include <linux/uio.h>
 #include <linux/uaccess.h>
 #include <keys/request_key_auth-type.h>
 #include "internal.h"
 
 #define KEY_MAX_DESC_SIZE 4096
 
 static const unsigned char keyrings_capabilities[2] = {
     [0] = (KEYCTL_CAPS0_CAPABILITIES |
            (IS_ENABLED(CONFIG_PERSISTENT_KEYRINGS)  ? KEYCTL_CAPS0_PERSISTENT_KEYRINGS : 0) |
            (IS_ENABLED(CONFIG_KEY_DH_OPERATIONS)    ? KEYCTL_CAPS0_DIFFIE_HELLMAN : 0) |
            (IS_ENABLED(CONFIG_ASYMMETRIC_KEY_TYPE)  ? KEYCTL_CAPS0_PUBLIC_KEY : 0) |
            (IS_ENABLED(CONFIG_BIG_KEYS)     ? KEYCTL_CAPS0_BIG_KEY : 0) |
            KEYCTL_CAPS0_INVALIDATE |
            KEYCTL_CAPS0_RESTRICT_KEYRING |
            KEYCTL_CAPS0_MOVE
            ),
     [1] = (KEYCTL_CAPS1_NS_KEYRING_NAME |
            KEYCTL_CAPS1_NS_KEY_TAG |
            (IS_ENABLED(CONFIG_KEY_NOTIFICATIONS)    ? KEYCTL_CAPS1_NOTIFICATIONS : 0)
            ),
 };
 
 static int key_get_type_from_user(char *type,
                   const char __user *_type,
                   unsigned len)
 {
     int ret;
 
     ret = strncpy_from_user(type, _type, len);
     if (ret < 0)
         return ret;
     if (ret == 0 || ret >= len)
         return -EINVAL;
     if (type[0] == '.')
         return -EPERM;
     type[len - 1] = '\0';
     return 0;
 }
 
 /*
  * Extract the description of a new key from userspace and either add it as a
  * new key to the specified keyring or update a matching key in that keyring.
  *
  * If the description is NULL or an empty string, the key type is asked to
  * generate one from the payload.
  *
  * The keyring must be writable so that we can attach the key to it.
  *
  * If successful, the new key's serial number is returned, otherwise an error
  * code is returned.
  */
 SYSCALL_DEFINE5(add_key, const char __user *, _type,
         const char __user *, _description,
         const void __user *, _payload,
         size_t, plen,
         key_serial_t, ringid)
 {
     key_ref_t keyring_ref, key_ref;
     char type[32], *description;
     void *payload;
     long ret;
 
     ret = -EINVAL;
     if (plen > 1024 * 1024 - 1)
         goto error;
 
     /* draw all the data into kernel space */
     ret = key_get_type_from_user(type, _type, sizeof(type));
     if (ret < 0)
         goto error;
 
     description = NULL;
     if (_description) {
         description = strndup_user(_description, KEY_MAX_DESC_SIZE);
         if (IS_ERR(description)) {
             ret = PTR_ERR(description);
             goto error;
         }
         if (!*description) {
             kfree(description);
             description = NULL;
         } else if ((description[0] == '.') &&
                (strncmp(type, "keyring", 7) == 0)) {
             ret = -EPERM;
             goto error2;
         }
     }
 
     /* pull the payload in if one was supplied */
     payload = NULL;
 
     if (plen) {
         ret = -ENOMEM;
         payload = kvmalloc(plen, GFP_KERNEL);
         if (!payload)
             goto error2;
 
         ret = -EFAULT;
         if (copy_from_user(payload, _payload, plen) != 0)
             goto error3;
     }
 
     /* find the target keyring (which must be writable) */
     keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
     if (IS_ERR(keyring_ref)) {
         ret = PTR_ERR(keyring_ref);
         goto error3;
     }
 
     /* create or update the requested key and add it to the target
      * keyring */
     key_ref = key_create_or_update(keyring_ref, type, description,
                        payload, plen, KEY_PERM_UNDEF,
                        KEY_ALLOC_IN_QUOTA);
     if (!IS_ERR(key_ref)) {
         ret = key_ref_to_ptr(key_ref)->serial;
         key_ref_put(key_ref);
     }
     else {
         ret = PTR_ERR(key_ref);
     }
 
     key_ref_put(keyring_ref);
  error3:
     kvfree_sensitive(payload, plen);
  error2:
     kfree(description);
  error:
     return ret;
 }
 
 /*
  * Search the process keyrings and keyring trees linked from those for a
  * matching key.  Keyrings must have appropriate Search permission to be
  * searched.
  *
  * If a key is found, it will be attached to the destination keyring if there's
  * one specified and the serial number of the key will be returned.
  *
  * If no key is found, /sbin/request-key will be invoked if _callout_info is
  * non-NULL in an attempt to create a key.  The _callout_info string will be
  * passed to /sbin/request-key to aid with completing the request.  If the
  * _callout_info string is "" then it will be changed to "-".
  */
 SYSCALL_DEFINE4(request_key, const char __user *, _type,
         const char __user *, _description,
         const char __user *, _callout_info,
         key_serial_t, destringid)
 {
     struct key_type *ktype;
     struct key *key;
     key_ref_t dest_ref;
     size_t callout_len;
     char type[32], *description, *callout_info;
     long ret;
 
     /* pull the type into kernel space */
     ret = key_get_type_from_user(type, _type, sizeof(type));
     if (ret < 0)
         goto error;
 
     /* pull the description into kernel space */
     description = strndup_user(_description, KEY_MAX_DESC_SIZE);
     if (IS_ERR(description)) {
         ret = PTR_ERR(description);
         goto error;
     }
 
     /* pull the callout info into kernel space */
     callout_info = NULL;
     callout_len = 0;
     if (_callout_info) {
         callout_info = strndup_user(_callout_info, PAGE_SIZE);
         if (IS_ERR(callout_info)) {
             ret = PTR_ERR(callout_info);
             goto error2;
         }
         callout_len = strlen(callout_info);
     }
 
     /* get the destination keyring if specified */
     dest_ref = NULL;
     if (destringid) {
         dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
                        KEY_NEED_WRITE);
         if (IS_ERR(dest_ref)) {
             ret = PTR_ERR(dest_ref);
             goto error3;
         }
     }
 
     /* find the key type */
     ktype = key_type_lookup(type);
     if (IS_ERR(ktype)) {
         ret = PTR_ERR(ktype);
         goto error4;
     }
 
     /* do the search */
     key = request_key_and_link(ktype, description, NULL, callout_info,
                    callout_len, NULL, key_ref_to_ptr(dest_ref),
                    KEY_ALLOC_IN_QUOTA);
     if (IS_ERR(key)) {
         ret = PTR_ERR(key);
         goto error5;
     }
 
     /* wait for the key to finish being constructed */
     ret = wait_for_key_construction(key, 1);
     if (ret < 0)
         goto error6;
 
     ret = key->serial;
 
 error6:
     key_put(key);
 error5:
     key_type_put(ktype);
 error4:
     key_ref_put(dest_ref);
 error3:
     kfree(callout_info);
 error2:
     kfree(description);
 error:
     return ret;
 }
 
 /*
  * Get the ID of the specified process keyring.
  *
  * The requested keyring must have search permission to be found.
  *
  * If successful, the ID of the requested keyring will be returned.
  */
 long keyctl_get_keyring_ID(key_serial_t id, int create)
 {
     key_ref_t key_ref;
     unsigned long lflags;
     long ret;
 
     lflags = create ? KEY_LOOKUP_CREATE : 0;
     key_ref = lookup_user_key(id, lflags, KEY_NEED_SEARCH);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
         goto error;
     }
 
     ret = key_ref_to_ptr(key_ref)->serial;
     key_ref_put(key_ref);
 error:
     return ret;
 }
 
 /*
  * Join a (named) session keyring.
  *
  * Create and join an anonymous session keyring or join a named session
  * keyring, creating it if necessary.  A named session keyring must have Search
  * permission for it to be joined.  Session keyrings without this permit will
  * be skipped over.  It is not permitted for userspace to create or join
  * keyrings whose name begin with a dot.
  *
  * If successful, the ID of the joined session keyring will be returned.
  */
 long keyctl_join_session_keyring(const char __user *_name)
 {
     char *name;
     long ret;
 
     /* fetch the name from userspace */
     name = NULL;
     if (_name) {
         name = strndup_user(_name, KEY_MAX_DESC_SIZE);
         if (IS_ERR(name)) {
             ret = PTR_ERR(name);
             goto error;
         }
 
         ret = -EPERM;
         if (name[0] == '.')
             goto error_name;
     }
 
     /* join the session */
     ret = join_session_keyring(name);
 error_name:
     kfree(name);
 error:
     return ret;
 }
 
 /*
  * Update a key's data payload from the given data.
  *
  * The key must grant the caller Write permission and the key type must support
  * updating for this to work.  A negative key can be positively instantiated
  * with this call.
  *
  * If successful, 0 will be returned.  If the key type does not support
  * updating, then -EOPNOTSUPP will be returned.
  */
 long keyctl_update_key(key_serial_t id,
                const void __user *_payload,
                size_t plen)
 {
     key_ref_t key_ref;
     void *payload;
     long ret;
 
     ret = -EINVAL;
     if (plen > PAGE_SIZE)
         goto error;
 
     /* pull the payload in if one was supplied */
     payload = NULL;
     if (plen) {
         ret = -ENOMEM;
         payload = kvmalloc(plen, GFP_KERNEL);
         if (!payload)
             goto error;
 
         ret = -EFAULT;
         if (copy_from_user(payload, _payload, plen) != 0)
             goto error2;
     }
 
     /* find the target key (which must be writable) */
     key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
         goto error2;
     }
 
     /* update the key */
     ret = key_update(key_ref, payload, plen);
 
     key_ref_put(key_ref);
 error2:
     kvfree_sensitive(payload, plen);
 error:
     return ret;
 }
 
 /*
  * Revoke a key.
  *
  * The key must be grant the caller Write or Setattr permission for this to
  * work.  The key type should give up its quota claim when revoked.  The key
  * and any links to the key will be automatically garbage collected after a
  * certain amount of time (/proc/sys/kernel/keys/gc_delay).
  *
  * Keys with KEY_FLAG_KEEP set should not be revoked.
  *
  * If successful, 0 is returned.
  */
 long keyctl_revoke_key(key_serial_t id)
 {
     key_ref_t key_ref;
     struct key *key;
     long ret;
 
     key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
         if (ret != -EACCES)
             goto error;
         key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
         if (IS_ERR(key_ref)) {
             ret = PTR_ERR(key_ref);
             goto error;
         }
     }
 
     key = key_ref_to_ptr(key_ref);
     ret = 0;
     if (test_bit(KEY_FLAG_KEEP, &key->flags))
         ret = -EPERM;
     else
         key_revoke(key);
 
     key_ref_put(key_ref);
 error:
     return ret;
 }
 
 /*
  * Invalidate a key.
  *
  * The key must be grant the caller Invalidate permission for this to work.
  * The key and any links to the key will be automatically garbage collected
  * immediately.
  *
  * Keys with KEY_FLAG_KEEP set should not be invalidated.
  *
  * If successful, 0 is returned.
  */
 long keyctl_invalidate_key(key_serial_t id)
 {
     key_ref_t key_ref;
     struct key *key;
     long ret;
 
     kenter("%d", id);
 
     key_ref = lookup_user_key(id, 0, KEY_NEED_SEARCH);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
 
         /* Root is permitted to invalidate certain special keys */
         if (capable(CAP_SYS_ADMIN)) {
             key_ref = lookup_user_key(id, 0, KEY_SYSADMIN_OVERRIDE);
             if (IS_ERR(key_ref))
                 goto error;
             if (test_bit(KEY_FLAG_ROOT_CAN_INVAL,
                      &key_ref_to_ptr(key_ref)->flags))
                 goto invalidate;
             goto error_put;
         }
 
         goto error;
     }
 
 invalidate:
     key = key_ref_to_ptr(key_ref);
     ret = 0;
     if (test_bit(KEY_FLAG_KEEP, &key->flags))
         ret = -EPERM;
     else
         key_invalidate(key);
 error_put:
     key_ref_put(key_ref);
 error:
     kleave(" = %ld", ret);
     return ret;
 }
 
 /*
  * Clear the specified keyring, creating an empty process keyring if one of the
  * special keyring IDs is used.
  *
  * The keyring must grant the caller Write permission and not have
  * KEY_FLAG_KEEP set for this to work.  If successful, 0 will be returned.
  */
 long keyctl_keyring_clear(key_serial_t ringid)
 {
     key_ref_t keyring_ref;
     struct key *keyring;
     long ret;
 
     keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
     if (IS_ERR(keyring_ref)) {
         ret = PTR_ERR(keyring_ref);
 
         /* Root is permitted to invalidate certain special keyrings */
         if (capable(CAP_SYS_ADMIN)) {
             keyring_ref = lookup_user_key(ringid, 0,
                               KEY_SYSADMIN_OVERRIDE);
             if (IS_ERR(keyring_ref))
                 goto error;
             if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
                      &key_ref_to_ptr(keyring_ref)->flags))
                 goto clear;
             goto error_put;
         }
 
         goto error;
     }
 
 clear:
     keyring = key_ref_to_ptr(keyring_ref);
     if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
         ret = -EPERM;
     else
         ret = keyring_clear(keyring);
 error_put:
     key_ref_put(keyring_ref);
 error:
     return ret;
 }
 
 /*
  * Create a link from a keyring to a key if there's no matching key in the
  * keyring, otherwise replace the link to the matching key with a link to the
  * new key.
  *
  * The key must grant the caller Link permission and the keyring must grant
  * the caller Write permission.  Furthermore, if an additional link is created,
  * the keyring's quota will be extended.
  *
  * If successful, 0 will be returned.
  */
 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, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
     if (IS_ERR(keyring_ref)) {
         ret = PTR_ERR(keyring_ref);
         goto error;
     }
 
     key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
         goto error2;
     }
 
     ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
 
     key_ref_put(key_ref);
 error2:
     key_ref_put(keyring_ref);
 error:
     return ret;
 }
 
 /*
  * Unlink a key from a keyring.
  *
  * The keyring must grant the caller Write permission for this to work; the key
  * itself need not grant the caller anything.  If the last link to a key is
  * removed then that key will be scheduled for destruction.
  *
  * Keys or keyrings with KEY_FLAG_KEEP set should not be unlinked.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
 {
     key_ref_t keyring_ref, key_ref;
     struct key *keyring, *key;
     long ret;
 
     keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_WRITE);
     if (IS_ERR(keyring_ref)) {
         ret = PTR_ERR(keyring_ref);
         goto error;
     }
 
     key_ref = lookup_user_key(id, KEY_LOOKUP_PARTIAL, KEY_NEED_UNLINK);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
         goto error2;
     }
 
     keyring = key_ref_to_ptr(keyring_ref);
     key = key_ref_to_ptr(key_ref);
     if (test_bit(KEY_FLAG_KEEP, &keyring->flags) &&
         test_bit(KEY_FLAG_KEEP, &key->flags))
         ret = -EPERM;
     else
         ret = key_unlink(keyring, key);
 
     key_ref_put(key_ref);
 error2:
     key_ref_put(keyring_ref);
 error:
     return ret;
 }
 
 /*
  * Move a link to a key from one keyring to another, displacing any matching
  * key from the destination keyring.
  *
  * The key must grant the caller Link permission and both keyrings must grant
  * the caller Write permission.  There must also be a link in the from keyring
  * to the key.  If both keyrings are the same, nothing is done.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_keyring_move(key_serial_t id, key_serial_t from_ringid,
              key_serial_t to_ringid, unsigned int flags)
 {
     key_ref_t key_ref, from_ref, to_ref;
     long ret;
 
     if (flags & ~KEYCTL_MOVE_EXCL)
         return -EINVAL;
 
     key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK);
     if (IS_ERR(key_ref))
         return PTR_ERR(key_ref);
 
     from_ref = lookup_user_key(from_ringid, 0, KEY_NEED_WRITE);
     if (IS_ERR(from_ref)) {
         ret = PTR_ERR(from_ref);
         goto error2;
     }
 
     to_ref = lookup_user_key(to_ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
     if (IS_ERR(to_ref)) {
         ret = PTR_ERR(to_ref);
         goto error3;
     }
 
     ret = key_move(key_ref_to_ptr(key_ref), key_ref_to_ptr(from_ref),
                key_ref_to_ptr(to_ref), flags);
 
     key_ref_put(to_ref);
 error3:
     key_ref_put(from_ref);
 error2:
     key_ref_put(key_ref);
     return ret;
 }
 
 /*
  * Return a description of a key to userspace.
  *
  * The key must grant the caller View permission for this to work.
  *
  * If there's a buffer, we place up to buflen bytes of data into it formatted
  * in the following way:
  *
  *  type;uid;gid;perm;description<NUL>
  *
  * If successful, we return the amount of description available, irrespective
  * of how much we may have copied into the buffer.
  */
 long keyctl_describe_key(key_serial_t keyid,
              char __user *buffer,
              size_t buflen)
 {
     struct key *key, *instkey;
     key_ref_t key_ref;
     char *infobuf;
     long ret;
     int desclen, infolen;
 
     key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
     if (IS_ERR(key_ref)) {
         /* viewing a key under construction is permitted if we have the
          * authorisation token handy */
         if (PTR_ERR(key_ref) == -EACCES) {
             instkey = key_get_instantiation_authkey(keyid);
             if (!IS_ERR(instkey)) {
                 key_put(instkey);
                 key_ref = lookup_user_key(keyid,
                               KEY_LOOKUP_PARTIAL,
                               KEY_AUTHTOKEN_OVERRIDE);
                 if (!IS_ERR(key_ref))
                     goto okay;
             }
         }
 
         ret = PTR_ERR(key_ref);
         goto error;
     }
 
 okay:
     key = key_ref_to_ptr(key_ref);
     desclen = strlen(key->description);
 
     /* calculate how much information we're going to return */
     ret = -ENOMEM;
     infobuf = kasprintf(GFP_KERNEL,
                 "%s;%d;%d;%08x;",
                 key->type->name,
                 from_kuid_munged(current_user_ns(), key->uid),
                 from_kgid_munged(current_user_ns(), key->gid),
                 key->perm);
     if (!infobuf)
         goto error2;
     infolen = strlen(infobuf);
     ret = infolen + desclen + 1;
 
     /* consider returning the data */
     if (buffer && buflen >= ret) {
         if (copy_to_user(buffer, infobuf, infolen) != 0 ||
             copy_to_user(buffer + infolen, key->description,
                  desclen + 1) != 0)
             ret = -EFAULT;
     }
 
     kfree(infobuf);
 error2:
     key_ref_put(key_ref);
 error:
     return ret;
 }
 
 /*
  * Search the specified keyring and any keyrings it links to for a matching
  * key.  Only keyrings that grant the caller Search permission will be searched
  * (this includes the starting keyring).  Only keys with Search permission can
  * be found.
  *
  * If successful, the found key will be linked to the destination keyring if
  * supplied and the key has Link permission, and the found key ID will be
  * returned.
  */
 long keyctl_keyring_search(key_serial_t ringid,
                const char __user *_type,
                const char __user *_description,
                key_serial_t destringid)
 {
     struct key_type *ktype;
     key_ref_t keyring_ref, key_ref, dest_ref;
     char type[32], *description;
     long ret;
 
     /* pull the type and description into kernel space */
     ret = key_get_type_from_user(type, _type, sizeof(type));
     if (ret < 0)
         goto error;
 
     description = strndup_user(_description, KEY_MAX_DESC_SIZE);
     if (IS_ERR(description)) {
         ret = PTR_ERR(description);
         goto error;
     }
 
     /* get the keyring at which to begin the search */
     keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_SEARCH);
     if (IS_ERR(keyring_ref)) {
         ret = PTR_ERR(keyring_ref);
         goto error2;
     }
 
     /* get the destination keyring if specified */
     dest_ref = NULL;
     if (destringid) {
         dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
                        KEY_NEED_WRITE);
         if (IS_ERR(dest_ref)) {
             ret = PTR_ERR(dest_ref);
             goto error3;
         }
     }
 
     /* find the key type */
     ktype = key_type_lookup(type);
     if (IS_ERR(ktype)) {
         ret = PTR_ERR(ktype);
         goto error4;
     }
 
     /* do the search */
     key_ref = keyring_search(keyring_ref, ktype, description, true);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
 
         /* treat lack or presence of a negative key the same */
         if (ret == -EAGAIN)
             ret = -ENOKEY;
         goto error5;
     }
 
     /* link the resulting key to the destination keyring if we can */
     if (dest_ref) {
         ret = key_permission(key_ref, KEY_NEED_LINK);
         if (ret < 0)
             goto error6;
 
         ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
         if (ret < 0)
             goto error6;
     }
 
     ret = key_ref_to_ptr(key_ref)->serial;
 
 error6:
     key_ref_put(key_ref);
 error5:
     key_type_put(ktype);
 error4:
     key_ref_put(dest_ref);
 error3:
     key_ref_put(keyring_ref);
 error2:
     kfree(description);
 error:
     return ret;
 }
 
 /*
  * Call the read method
  */
 static long __keyctl_read_key(struct key *key, char *buffer, size_t buflen)
 {
     long ret;
 
     down_read(&key->sem);
     ret = key_validate(key);
     if (ret == 0)
         ret = key->type->read(key, buffer, buflen);
     up_read(&key->sem);
     return ret;
 }
 
 /*
  * Read a key's payload.
  *
  * The key must either grant the caller Read permission, or it must grant the
  * caller Search permission when searched for from the process keyrings.
  *
  * If successful, we place up to buflen bytes of data into the buffer, if one
  * is provided, and return the amount of data that is available in the key,
  * irrespective of how much we copied into the buffer.
  */
 long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
 {
     struct key *key;
     key_ref_t key_ref;
     long ret;
     char *key_data = NULL;
     size_t key_data_len;
 
     /* find the key first */
     key_ref = lookup_user_key(keyid, 0, KEY_DEFER_PERM_CHECK);
     if (IS_ERR(key_ref)) {
         ret = -ENOKEY;
         goto out;
     }
 
     key = key_ref_to_ptr(key_ref);
 
     ret = key_read_state(key);
     if (ret < 0)
         goto key_put_out; /* Negatively instantiated */
 
     /* see if we can read it directly */
     ret = key_permission(key_ref, KEY_NEED_READ);
     if (ret == 0)
         goto can_read_key;
     if (ret != -EACCES)
         goto key_put_out;
 
     /* we can't; see if it's searchable from this process's keyrings
      * - we automatically take account of the fact that it may be
      *   dangling off an instantiation key
      */
     if (!is_key_possessed(key_ref)) {
         ret = -EACCES;
         goto key_put_out;
     }
 
     /* the key is probably readable - now try to read it */
 can_read_key:
     if (!key->type->read) {
         ret = -EOPNOTSUPP;
         goto key_put_out;
     }
 
     if (!buffer || !buflen) {
         /* Get the key length from the read method */
         ret = __keyctl_read_key(key, NULL, 0);
         goto key_put_out;
     }
 
     /*
      * Read the data with the semaphore held (since we might sleep)
      * to protect against the key being updated or revoked.
      *
      * Allocating a temporary buffer to hold the keys before
      * transferring them to user buffer to avoid potential
      * deadlock involving page fault and mmap_lock.
      *
      * key_data_len = (buflen <= PAGE_SIZE)
      *      ? buflen : actual length of key data
      *
      * This prevents allocating arbitrary large buffer which can
      * be much larger than the actual key length. In the latter case,
      * at least 2 passes of this loop is required.
      */
     key_data_len = (buflen <= PAGE_SIZE) ? buflen : 0;
     for (;;) {
         if (key_data_len) {
             key_data = kvmalloc(key_data_len, GFP_KERNEL);
             if (!key_data) {
                 ret = -ENOMEM;
                 goto key_put_out;
             }
         }
 
         ret = __keyctl_read_key(key, key_data, key_data_len);
 
         /*
          * Read methods will just return the required length without
          * any copying if the provided length isn't large enough.
          */
         if (ret <= 0 || ret > buflen)
             break;
 
         /*
          * The key may change (unlikely) in between 2 consecutive
          * __keyctl_read_key() calls. In this case, we reallocate
          * a larger buffer and redo the key read when
          * key_data_len < ret <= buflen.
          */
         if (ret > key_data_len) {
             if (unlikely(key_data))
                 kvfree_sensitive(key_data, key_data_len);
             key_data_len = ret;
             continue;   /* Allocate buffer */
         }
 
         if (copy_to_user(buffer, key_data, ret))
             ret = -EFAULT;
         break;
     }
     kvfree_sensitive(key_data, key_data_len);
 
 key_put_out:
     key_put(key);
 out:
     return ret;
 }
 
 /*
  * Change the ownership of a key
  *
  * The key must grant the caller Setattr permission for this to work, though
  * the key need not be fully instantiated yet.  For the UID to be changed, or
  * for the GID to be changed to a group the caller is not a member of, the
  * caller must have sysadmin capability.  If either uid or gid is -1 then that
  * attribute is not changed.
  *
  * If the UID is to be changed, the new user must have sufficient quota to
  * accept the key.  The quota deduction will be removed from the old user to
  * the new user should the attribute be changed.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
 {
     struct key_user *newowner, *zapowner = NULL;
     struct key *key;
     key_ref_t key_ref;
     long ret;
     kuid_t uid;
     kgid_t gid;
 
     uid = make_kuid(current_user_ns(), user);
     gid = make_kgid(current_user_ns(), group);
     ret = -EINVAL;
     if ((user != (uid_t) -1) && !uid_valid(uid))
         goto error;
     if ((group != (gid_t) -1) && !gid_valid(gid))
         goto error;
 
     ret = 0;
     if (user == (uid_t) -1 && group == (gid_t) -1)
         goto error;
 
     key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                   KEY_NEED_SETATTR);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
         goto error;
     }
 
     key = key_ref_to_ptr(key_ref);
 
     /* make the changes with the locks held to prevent chown/chown races */
     ret = -EACCES;
     down_write(&key->sem);
 
     if (!capable(CAP_SYS_ADMIN)) {
         /* only the sysadmin can chown a key to some other UID */
         if (user != (uid_t) -1 && !uid_eq(key->uid, uid))
             goto error_put;
 
         /* only the sysadmin can set the key's GID to a group other
          * than one of those that the current process subscribes to */
         if (group != (gid_t) -1 && !gid_eq(gid, key->gid) && !in_group_p(gid))
             goto error_put;
     }
 
     /* change the UID */
     if (user != (uid_t) -1 && !uid_eq(uid, key->uid)) {
         ret = -ENOMEM;
         newowner = key_user_lookup(uid);
         if (!newowner)
             goto error_put;
 
         /* transfer the quota burden to the new user */
         if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
             unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
                 key_quota_root_maxkeys : key_quota_maxkeys;
             unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
                 key_quota_root_maxbytes : key_quota_maxbytes;
 
             spin_lock(&newowner->lock);
             if (newowner->qnkeys + 1 > maxkeys ||
                 newowner->qnbytes + key->quotalen > maxbytes ||
                 newowner->qnbytes + key->quotalen <
                 newowner->qnbytes)
                 goto quota_overrun;
 
             newowner->qnkeys++;
             newowner->qnbytes += key->quotalen;
             spin_unlock(&newowner->lock);
 
             spin_lock(&key->user->lock);
             key->user->qnkeys--;
             key->user->qnbytes -= key->quotalen;
             spin_unlock(&key->user->lock);
         }
 
         atomic_dec(&key->user->nkeys);
         atomic_inc(&newowner->nkeys);
 
         if (key->state != KEY_IS_UNINSTANTIATED) {
             atomic_dec(&key->user->nikeys);
             atomic_inc(&newowner->nikeys);
         }
 
         zapowner = key->user;
         key->user = newowner;
         key->uid = uid;
     }
 
     /* change the GID */
     if (group != (gid_t) -1)
         key->gid = gid;
 
     notify_key(key, NOTIFY_KEY_SETATTR, 0);
     ret = 0;
 
 error_put:
     up_write(&key->sem);
     key_put(key);
     if (zapowner)
         key_user_put(zapowner);
 error:
     return ret;
 
 quota_overrun:
     spin_unlock(&newowner->lock);
     zapowner = newowner;
     ret = -EDQUOT;
     goto error_put;
 }
 
 /*
  * Change the permission mask on a key.
  *
  * The key must grant the caller Setattr permission for this to work, though
  * the key need not be fully instantiated yet.  If the caller does not have
  * sysadmin capability, it may only change the permission on keys that it owns.
  */
 long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
 {
     struct key *key;
     key_ref_t key_ref;
     long ret;
 
     ret = -EINVAL;
     if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
         goto error;
 
     key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                   KEY_NEED_SETATTR);
     if (IS_ERR(key_ref)) {
         ret = PTR_ERR(key_ref);
         goto error;
     }
 
     key = key_ref_to_ptr(key_ref);
 
     /* make the changes with the locks held to prevent chown/chmod races */
     ret = -EACCES;
     down_write(&key->sem);
 
     /* if we're not the sysadmin, we can only change a key that we own */
     if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
         key->perm = perm;
         notify_key(key, NOTIFY_KEY_SETATTR, 0);
         ret = 0;
     }
 
     up_write(&key->sem);
     key_put(key);
 error:
     return ret;
 }
 
 /*
  * Get the destination keyring for instantiation and check that the caller has
  * Write permission on it.
  */
 static long get_instantiation_keyring(key_serial_t ringid,
                       struct request_key_auth *rka,
                       struct key **_dest_keyring)
 {
     key_ref_t dkref;
 
     *_dest_keyring = NULL;
 
     /* just return a NULL pointer if we weren't asked to make a link */
     if (ringid == 0)
         return 0;
 
     /* if a specific keyring is nominated by ID, then use that */
     if (ringid > 0) {
         dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
         if (IS_ERR(dkref))
             return PTR_ERR(dkref);
         *_dest_keyring = key_ref_to_ptr(dkref);
         return 0;
     }
 
     if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
         return -EINVAL;
 
     /* otherwise specify the destination keyring recorded in the
      * authorisation key (any KEY_SPEC_*_KEYRING) */
     if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
         *_dest_keyring = key_get(rka->dest_keyring);
         return 0;
     }
 
     return -ENOKEY;
 }
 
 /*
  * Change the request_key authorisation key on the current process.
  */
 static int keyctl_change_reqkey_auth(struct key *key)
 {
     struct cred *new;
 
     new = prepare_creds();
     if (!new)
         return -ENOMEM;
 
     key_put(new->request_key_auth);
     new->request_key_auth = key_get(key);
 
     return commit_creds(new);
 }
 
 /*
  * Instantiate a key with the specified payload and link the key into the
  * destination keyring if one is given.
  *
  * The caller must have the appropriate instantiation permit set for this to
  * work (see keyctl_assume_authority).  No other permissions are required.
  *
  * If successful, 0 will be returned.
  */
 static long keyctl_instantiate_key_common(key_serial_t id,
                    struct iov_iter *from,
                    key_serial_t ringid)
 {
     const struct cred *cred = current_cred();
     struct request_key_auth *rka;
     struct key *instkey, *dest_keyring;
     size_t plen = from ? iov_iter_count(from) : 0;
     void *payload;
     long ret;
 
     kenter("%d,,%zu,%d", id, plen, ringid);
 
     if (!plen)
         from = NULL;
 
     ret = -EINVAL;
     if (plen > 1024 * 1024 - 1)
         goto error;
 
     /* the appropriate instantiation authorisation key must have been
      * assumed before calling this */
     ret = -EPERM;
     instkey = cred->request_key_auth;
     if (!instkey)
         goto error;
 
     rka = instkey->payload.data[0];
     if (rka->target_key->serial != id)
         goto error;
 
     /* pull the payload in if one was supplied */
     payload = NULL;
 
     if (from) {
         ret = -ENOMEM;
         payload = kvmalloc(plen, GFP_KERNEL);
         if (!payload)
             goto error;
 
         ret = -EFAULT;
         if (!copy_from_iter_full(payload, plen, from))
             goto error2;
     }
 
     /* find the destination keyring amongst those belonging to the
      * requesting task */
     ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
     if (ret < 0)
         goto error2;
 
     /* instantiate the key and link it into a keyring */
     ret = key_instantiate_and_link(rka->target_key, payload, plen,
                        dest_keyring, instkey);
 
     key_put(dest_keyring);
 
     /* discard the assumed authority if it's just been disabled by
      * instantiation of the key */
     if (ret == 0)
         keyctl_change_reqkey_auth(NULL);
 
 error2:
     kvfree_sensitive(payload, plen);
 error:
     return ret;
 }
 
 /*
  * Instantiate a key with the specified payload and link the key into the
  * destination keyring if one is given.
  *
  * The caller must have the appropriate instantiation permit set for this to
  * work (see keyctl_assume_authority).  No other permissions are required.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_instantiate_key(key_serial_t id,
                 const void __user *_payload,
                 size_t plen,
                 key_serial_t ringid)
 {
     if (_payload && plen) {
         struct iovec iov;
         struct iov_iter from;
         int ret;
 
         ret = import_single_range(WRITE, (void __user *)_payload, plen,
                       &iov, &from);
         if (unlikely(ret))
             return ret;
 
         return keyctl_instantiate_key_common(id, &from, ringid);
     }
 
     return keyctl_instantiate_key_common(id, NULL, ringid);
 }
 
 /*
  * Instantiate a key with the specified multipart payload and link the key into
  * the destination keyring if one is given.
  *
  * The caller must have the appropriate instantiation permit set for this to
  * work (see keyctl_assume_authority).  No other permissions are required.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_instantiate_key_iov(key_serial_t id,
                 const struct iovec __user *_payload_iov,
                 unsigned ioc,
                 key_serial_t ringid)
 {
     struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
     struct iov_iter from;
     long ret;
 
     if (!_payload_iov)
         ioc = 0;
 
     ret = import_iovec(WRITE, _payload_iov, ioc,
                     ARRAY_SIZE(iovstack), &iov, &from);
     if (ret < 0)
         return ret;
     ret = keyctl_instantiate_key_common(id, &from, ringid);
     kfree(iov);
     return ret;
 }
 
 /*
  * Negatively instantiate the key with the given timeout (in seconds) and link
  * the key into the destination keyring if one is given.
  *
  * The caller must have the appropriate instantiation permit set for this to
  * work (see keyctl_assume_authority).  No other permissions are required.
  *
  * The key and any links to the key will be automatically garbage collected
  * after the timeout expires.
  *
  * Negative keys are used to rate limit repeated request_key() calls by causing
  * them to return -ENOKEY until the negative key expires.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
 {
     return keyctl_reject_key(id, timeout, ENOKEY, ringid);
 }
 
 /*
  * Negatively instantiate the key with the given timeout (in seconds) and error
  * code and link the key into the destination keyring if one is given.
  *
  * The caller must have the appropriate instantiation permit set for this to
  * work (see keyctl_assume_authority).  No other permissions are required.
  *
  * The key and any links to the key will be automatically garbage collected
  * after the timeout expires.
  *
  * Negative keys are used to rate limit repeated request_key() calls by causing
  * them to return the specified error code until the negative key expires.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
                key_serial_t ringid)
 {
     const struct cred *cred = current_cred();
     struct request_key_auth *rka;
     struct key *instkey, *dest_keyring;
     long ret;
 
     kenter("%d,%u,%u,%d", id, timeout, error, ringid);
 
     /* must be a valid error code and mustn't be a kernel special */
     if (error <= 0 ||
         error >= MAX_ERRNO ||
         error == ERESTARTSYS ||
         error == ERESTARTNOINTR ||
         error == ERESTARTNOHAND ||
         error == ERESTART_RESTARTBLOCK)
         return -EINVAL;
 
     /* the appropriate instantiation authorisation key must have been
      * assumed before calling this */
     ret = -EPERM;
     instkey = cred->request_key_auth;
     if (!instkey)
         goto error;
 
     rka = instkey->payload.data[0];
     if (rka->target_key->serial != id)
         goto error;
 
     /* find the destination keyring if present (which must also be
      * writable) */
     ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
     if (ret < 0)
         goto error;
 
     /* instantiate the key and link it into a keyring */
     ret = key_reject_and_link(rka->target_key, timeout, error,
                   dest_keyring, instkey);
 
     key_put(dest_keyring);
 
     /* discard the assumed authority if it's just been disabled by
      * instantiation of the key */
     if (ret == 0)
         keyctl_change_reqkey_auth(NULL);
 
 error:
     return ret;
 }
 
 /*
  * Read or set the default keyring in which request_key() will cache keys and
  * return the old setting.
  *
  * If a thread or process keyring is specified then it will be created if it
  * doesn't yet exist.  The old setting will be returned if successful.
  */
 long keyctl_set_reqkey_keyring(int reqkey_defl)
 {
     struct cred *new;
     int ret, old_setting;
 
     old_setting = current_cred_xxx(jit_keyring);
 
     if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
         return old_setting;
 
     new = prepare_creds();
     if (!new)
         return -ENOMEM;
 
     switch (reqkey_defl) {
     case KEY_REQKEY_DEFL_THREAD_KEYRING:
         ret = install_thread_keyring_to_cred(new);
         if (ret < 0)
             goto error;
         goto set;
 
     case KEY_REQKEY_DEFL_PROCESS_KEYRING:
         ret = install_process_keyring_to_cred(new);
         if (ret < 0)
             goto error;
         goto set;
 
     case KEY_REQKEY_DEFL_DEFAULT:
     case KEY_REQKEY_DEFL_SESSION_KEYRING:
     case KEY_REQKEY_DEFL_USER_KEYRING:
     case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
     case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
         goto set;
 
     case KEY_REQKEY_DEFL_NO_CHANGE:
     case KEY_REQKEY_DEFL_GROUP_KEYRING:
     default:
         ret = -EINVAL;
         goto error;
     }
 
 set:
     new->jit_keyring = reqkey_defl;
     commit_creds(new);
     return old_setting;
 error:
     abort_creds(new);
     return ret;
 }
 
 /*
  * Set or clear the timeout on a key.
  *
  * Either the key must grant the caller Setattr permission or else the caller
  * must hold an instantiation authorisation token for the key.
  *
  * The timeout is either 0 to clear the timeout, or a number of seconds from
  * the current time.  The key and any links to the key will be automatically
  * garbage collected after the timeout expires.
  *
  * Keys with KEY_FLAG_KEEP set should not be timed out.
  *
  * If successful, 0 is returned.
  */
 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
 {
     struct key *key, *instkey;
     key_ref_t key_ref;
     long ret;
 
     key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
                   KEY_NEED_SETATTR);
     if (IS_ERR(key_ref)) {
         /* setting the timeout on a key under construction is permitted
          * if we have the authorisation token handy */
         if (PTR_ERR(key_ref) == -EACCES) {
             instkey = key_get_instantiation_authkey(id);
             if (!IS_ERR(instkey)) {
                 key_put(instkey);
                 key_ref = lookup_user_key(id,
                               KEY_LOOKUP_PARTIAL,
                               KEY_AUTHTOKEN_OVERRIDE);
                 if (!IS_ERR(key_ref))
                     goto okay;
             }
         }
 
         ret = PTR_ERR(key_ref);
         goto error;
     }
 
 okay:
     key = key_ref_to_ptr(key_ref);
     ret = 0;
     if (test_bit(KEY_FLAG_KEEP, &key->flags)) {
         ret = -EPERM;
     } else {
         key_set_timeout(key, timeout);
         notify_key(key, NOTIFY_KEY_SETATTR, 0);
     }
     key_put(key);
 
 error:
     return ret;
 }
 
 /*
  * Assume (or clear) the authority to instantiate the specified key.
  *
  * This sets the authoritative token currently in force for key instantiation.
  * This must be done for a key to be instantiated.  It has the effect of making
  * available all the keys from the caller of the request_key() that created a
  * key to request_key() calls made by the caller of this function.
  *
  * The caller must have the instantiation key in their process keyrings with a
  * Search permission grant available to the caller.
  *
  * If the ID given is 0, then the setting will be cleared and 0 returned.
  *
  * If the ID given has a matching an authorisation key, then that key will be
  * set and its ID will be returned.  The authorisation key can be read to get
  * the callout information passed to request_key().
  */
 long keyctl_assume_authority(key_serial_t id)
 {
     struct key *authkey;
     long ret;
 
     /* special key IDs aren't permitted */
     ret = -EINVAL;
     if (id < 0)
         goto error;
 
     /* we divest ourselves of authority if given an ID of 0 */
     if (id == 0) {
         ret = keyctl_change_reqkey_auth(NULL);
         goto error;
     }
 
     /* attempt to assume the authority temporarily granted to us whilst we
      * instantiate the specified key
      * - the authorisation key must be in the current task's keyrings
      *   somewhere
      */
     authkey = key_get_instantiation_authkey(id);
     if (IS_ERR(authkey)) {
         ret = PTR_ERR(authkey);
         goto error;
     }
 
     ret = keyctl_change_reqkey_auth(authkey);
     if (ret == 0)
         ret = authkey->serial;
     key_put(authkey);
 error:
     return ret;
 }
 
 /*
  * Get a key's the LSM security label.
  *
  * The key must grant the caller View permission for this to work.
  *
  * If there's a buffer, then up to buflen bytes of data will be placed into it.
  *
  * If successful, the amount of information available will be returned,
  * irrespective of how much was copied (including the terminal NUL).
  */
 long keyctl_get_security(key_serial_t keyid,
              char __user *buffer,
              size_t buflen)
 {
     struct key *key, *instkey;
     key_ref_t key_ref;
     char *context;
     long ret;
 
     key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
     if (IS_ERR(key_ref)) {
         if (PTR_ERR(key_ref) != -EACCES)
             return PTR_ERR(key_ref);
 
         /* viewing a key under construction is also permitted if we
          * have the authorisation token handy */
         instkey = key_get_instantiation_authkey(keyid);
         if (IS_ERR(instkey))
             return PTR_ERR(instkey);
         key_put(instkey);
 
         key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL,
                       KEY_AUTHTOKEN_OVERRIDE);
         if (IS_ERR(key_ref))
             return PTR_ERR(key_ref);
     }
 
     key = key_ref_to_ptr(key_ref);
     ret = security_key_getsecurity(key, &context);
     if (ret == 0) {
         /* if no information was returned, give userspace an empty
          * string */
         ret = 1;
         if (buffer && buflen > 0 &&
             copy_to_user(buffer, "", 1) != 0)
             ret = -EFAULT;
     } else if (ret > 0) {
         /* return as much data as there's room for */
         if (buffer && buflen > 0) {
             if (buflen > ret)
                 buflen = ret;
 
             if (copy_to_user(buffer, context, buflen) != 0)
                 ret = -EFAULT;
         }
 
         kfree(context);
     }
 
     key_ref_put(key_ref);
     return ret;
 }
 
 /*
  * Attempt to install the calling process's session keyring on the process's
  * parent process.
  *
  * The keyring must exist and must grant the caller LINK permission, and the
  * parent process must be single-threaded and must have the same effective
  * ownership as this process and mustn't be SUID/SGID.
  *
  * The keyring will be emplaced on the parent when it next resumes userspace.
  *
  * If successful, 0 will be returned.
  */
 long keyctl_session_to_parent(void)
 {
     struct task_struct *me, *parent;
     const struct cred *mycred, *pcred;
     struct callback_head *newwork, *oldwork;
     key_ref_t keyring_r;
     struct cred *cred;
     int ret;
 
     keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_NEED_LINK);
     if (IS_ERR(keyring_r))
         return PTR_ERR(keyring_r);
 
     ret = -ENOMEM;
 
     /* our parent is going to need a new cred struct, a new tgcred struct
      * and new security data, so we allocate them here to prevent ENOMEM in
      * our parent */
     cred = cred_alloc_blank();
     if (!cred)
         goto error_keyring;
     newwork = &cred->rcu;
 
     cred->session_keyring = key_ref_to_ptr(keyring_r);
     keyring_r = NULL;
     init_task_work(newwork, key_change_session_keyring);
 
     me = current;
     rcu_read_lock();
     write_lock_irq(&tasklist_lock);
 
     ret = -EPERM;
     oldwork = NULL;
     parent = rcu_dereference_protected(me->real_parent,
                        lockdep_is_held(&tasklist_lock));
 
     /* the parent mustn't be init and mustn't be a kernel thread */
     if (parent->pid <= 1 || !parent->mm)
         goto unlock;
 
     /* the parent must be single threaded */
     if (!thread_group_empty(parent))
         goto unlock;
 
     /* the parent and the child must have different session keyrings or
      * there's no point */
     mycred = current_cred();
     pcred = __task_cred(parent);
     if (mycred == pcred ||
         mycred->session_keyring == pcred->session_keyring) {
         ret = 0;
         goto unlock;
     }
 
     /* the parent must have the same effective ownership and mustn't be
      * SUID/SGID */
     if (!uid_eq(pcred->uid,  mycred->euid) ||
         !uid_eq(pcred->euid, mycred->euid) ||
         !uid_eq(pcred->suid, mycred->euid) ||
         !gid_eq(pcred->gid,  mycred->egid) ||
         !gid_eq(pcred->egid, mycred->egid) ||
         !gid_eq(pcred->sgid, mycred->egid))
         goto unlock;
 
     /* the keyrings must have the same UID */
     if ((pcred->session_keyring &&
          !uid_eq(pcred->session_keyring->uid, mycred->euid)) ||
         !uid_eq(mycred->session_keyring->uid, mycred->euid))
         goto unlock;
 
     /* cancel an already pending keyring replacement */
     oldwork = task_work_cancel(parent, key_change_session_keyring);
 
     /* the replacement session keyring is applied just prior to userspace
      * restarting */
     ret = task_work_add(parent, newwork, TWA_RESUME);
     if (!ret)
         newwork = NULL;
 unlock:
     write_unlock_irq(&tasklist_lock);
     rcu_read_unlock();
     if (oldwork)
         put_cred(container_of(oldwork, struct cred, rcu));
     if (newwork)
         put_cred(cred);
     return ret;
 
 error_keyring:
     key_ref_put(keyring_r);
     return ret;
 }
 
 /*
  * Apply a restriction to a given keyring.
  *
  * The caller must have Setattr permission to change keyring restrictions.
  *
  * The requested type name may be a NULL pointer to reject all attempts
  * to link to the keyring.  In this case, _restriction must also be NULL.
  * Otherwise, both _type and _restriction must be non-NULL.
  *
  * Returns 0 if successful.
  */
 long keyctl_restrict_keyring(key_serial_t id, const char __user *_type,
                  const char __user *_restriction)
 {
     key_ref_t key_ref;
     char type[32];
     char *restriction = NULL;
     long ret;
 
     key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
     if (IS_ERR(key_ref))
         return PTR_ERR(key_ref);
 
     ret = -EINVAL;
     if (_type) {
         if (!_restriction)
             goto error;
 
         ret = key_get_type_from_user(type, _type, sizeof(type));
         if (ret < 0)
             goto error;
 
         restriction = strndup_user(_restriction, PAGE_SIZE);
         if (IS_ERR(restriction)) {
             ret = PTR_ERR(restriction);
             goto error;
         }
     } else {
         if (_restriction)
             goto error;
     }
 
     ret = keyring_restrict(key_ref, _type ? type : NULL, restriction);
     kfree(restriction);
 error:
     key_ref_put(key_ref);
     return ret;
 }
 
 #ifdef CONFIG_KEY_NOTIFICATIONS
 /*
  * Watch for changes to a key.
  *
  * The caller must have View permission to watch a key or keyring.
  */
 long keyctl_watch_key(key_serial_t id, int watch_queue_fd, int watch_id)
 {
     struct watch_queue *wqueue;
     struct watch_list *wlist = NULL;
     struct watch *watch = NULL;
     struct key *key;
     key_ref_t key_ref;
     long ret;
 
     if (watch_id < -1 || watch_id > 0xff)
         return -EINVAL;
 
     key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_VIEW);
     if (IS_ERR(key_ref))
         return PTR_ERR(key_ref);
     key = key_ref_to_ptr(key_ref);
 
     wqueue = get_watch_queue(watch_queue_fd);
     if (IS_ERR(wqueue)) {
         ret = PTR_ERR(wqueue);
         goto err_key;
     }
 
     if (watch_id >= 0) {
         ret = -ENOMEM;
         if (!key->watchers) {
             wlist = kzalloc(sizeof(*wlist), GFP_KERNEL);
             if (!wlist)
                 goto err_wqueue;
             init_watch_list(wlist, NULL);
         }
 
         watch = kzalloc(sizeof(*watch), GFP_KERNEL);
         if (!watch)
             goto err_wlist;
 
         init_watch(watch, wqueue);
         watch->id   = key->serial;
         watch->info_id  = (u32)watch_id << WATCH_INFO_ID__SHIFT;
 
         ret = security_watch_key(key);
         if (ret < 0)
             goto err_watch;
 
         down_write(&key->sem);
         if (!key->watchers) {
             key->watchers = wlist;
             wlist = NULL;
         }
 
         ret = add_watch_to_object(watch, key->watchers);
         up_write(&key->sem);
 
         if (ret == 0)
             watch = NULL;
     } else {
         ret = -EBADSLT;
         if (key->watchers) {
             down_write(&key->sem);
             ret = remove_watch_from_object(key->watchers,
                                wqueue, key_serial(key),
                                false);
             up_write(&key->sem);
         }
     }
 
 err_watch:
     kfree(watch);
 err_wlist:
     kfree(wlist);
 err_wqueue:
     put_watch_queue(wqueue);
 err_key:
     key_put(key);
     return ret;
 }
 #endif /* CONFIG_KEY_NOTIFICATIONS */
 
 /*
  * Get keyrings subsystem capabilities.
  */
 long keyctl_capabilities(unsigned char __user *_buffer, size_t buflen)
 {
     size_t size = buflen;
 
     if (size > 0) {
         if (size > sizeof(keyrings_capabilities))
             size = sizeof(keyrings_capabilities);
         if (copy_to_user(_buffer, keyrings_capabilities, size) != 0)
             return -EFAULT;
         if (size < buflen &&
             clear_user(_buffer + size, buflen - size) != 0)
             return -EFAULT;
     }
 
     return sizeof(keyrings_capabilities);
 }
 
 /*
  * The key control system call
  */
 SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
         unsigned long, arg4, unsigned long, arg5)
 {
     switch (option) {
     case KEYCTL_GET_KEYRING_ID:
         return keyctl_get_keyring_ID((key_serial_t) arg2,
                          (int) arg3);
 
     case KEYCTL_JOIN_SESSION_KEYRING:
         return keyctl_join_session_keyring((const char __user *) arg2);
 
     case KEYCTL_UPDATE:
         return keyctl_update_key((key_serial_t) arg2,
                      (const void __user *) arg3,
                      (size_t) arg4);
 
     case KEYCTL_REVOKE:
         return keyctl_revoke_key((key_serial_t) arg2);
 
     case KEYCTL_DESCRIBE:
         return keyctl_describe_key((key_serial_t) arg2,
                        (char __user *) arg3,
                        (unsigned) arg4);
 
     case KEYCTL_CLEAR:
         return keyctl_keyring_clear((key_serial_t) arg2);
 
     case KEYCTL_LINK:
         return keyctl_keyring_link((key_serial_t) arg2,
                        (key_serial_t) arg3);
 
     case KEYCTL_UNLINK:
         return keyctl_keyring_unlink((key_serial_t) arg2,
                          (key_serial_t) arg3);
 
     case KEYCTL_SEARCH:
         return keyctl_keyring_search((key_serial_t) arg2,
                          (const char __user *) arg3,
                          (const char __user *) arg4,
                          (key_serial_t) arg5);
 
     case KEYCTL_READ:
         return keyctl_read_key((key_serial_t) arg2,
                        (char __user *) arg3,
                        (size_t) arg4);
 
     case KEYCTL_CHOWN:
         return keyctl_chown_key((key_serial_t) arg2,
                     (uid_t) arg3,
                     (gid_t) arg4);
 
     case KEYCTL_SETPERM:
         return keyctl_setperm_key((key_serial_t) arg2,
                       (key_perm_t) arg3);
 
     case KEYCTL_INSTANTIATE:
         return keyctl_instantiate_key((key_serial_t) arg2,
                           (const void __user *) arg3,
                           (size_t) arg4,
                           (key_serial_t) arg5);
 
     case KEYCTL_NEGATE:
         return keyctl_negate_key((key_serial_t) arg2,
                      (unsigned) arg3,
                      (key_serial_t) arg4);
 
     case KEYCTL_SET_REQKEY_KEYRING:
         return keyctl_set_reqkey_keyring(arg2);
 
     case KEYCTL_SET_TIMEOUT:
         return keyctl_set_timeout((key_serial_t) arg2,
                       (unsigned) arg3);
 
     case KEYCTL_ASSUME_AUTHORITY:
         return keyctl_assume_authority((key_serial_t) arg2);
 
     case KEYCTL_GET_SECURITY:
         return keyctl_get_security((key_serial_t) arg2,
                        (char __user *) arg3,
                        (size_t) arg4);
 
     case KEYCTL_SESSION_TO_PARENT:
         return keyctl_session_to_parent();
 
     case KEYCTL_REJECT:
         return keyctl_reject_key((key_serial_t) arg2,
                      (unsigned) arg3,
                      (unsigned) arg4,
                      (key_serial_t) arg5);
 
     case KEYCTL_INSTANTIATE_IOV:
         return keyctl_instantiate_key_iov(
             (key_serial_t) arg2,
             (const struct iovec __user *) arg3,
             (unsigned) arg4,
             (key_serial_t) arg5);
 
     case KEYCTL_INVALIDATE:
         return keyctl_invalidate_key((key_serial_t) arg2);
 
     case KEYCTL_GET_PERSISTENT:
         return keyctl_get_persistent((uid_t)arg2, (key_serial_t)arg3);
 
     case KEYCTL_DH_COMPUTE:
         return keyctl_dh_compute((struct keyctl_dh_params __user *) arg2,
                      (char __user *) arg3, (size_t) arg4,
                      (struct keyctl_kdf_params __user *) arg5);
 
     case KEYCTL_RESTRICT_KEYRING:
         return keyctl_restrict_keyring((key_serial_t) arg2,
                            (const char __user *) arg3,
                            (const char __user *) arg4);
 
     case KEYCTL_PKEY_QUERY:
         if (arg3 != 0)
             return -EINVAL;
         return keyctl_pkey_query((key_serial_t)arg2,
                      (const char __user *)arg4,
                      (struct keyctl_pkey_query __user *)arg5);
 
     case KEYCTL_PKEY_ENCRYPT:
     case KEYCTL_PKEY_DECRYPT:
     case KEYCTL_PKEY_SIGN:
         return keyctl_pkey_e_d_s(
             option,
             (const struct keyctl_pkey_params __user *)arg2,
             (const char __user *)arg3,
             (const void __user *)arg4,
             (void __user *)arg5);
 
     case KEYCTL_PKEY_VERIFY:
         return keyctl_pkey_verify(
             (const struct keyctl_pkey_params __user *)arg2,
             (const char __user *)arg3,
             (const void __user *)arg4,
             (const void __user *)arg5);
 
     case KEYCTL_MOVE:
         return keyctl_keyring_move((key_serial_t)arg2,
                        (key_serial_t)arg3,
                        (key_serial_t)arg4,
                        (unsigned int)arg5);
 
     case KEYCTL_CAPABILITIES:
         return keyctl_capabilities((unsigned char __user *)arg2, (size_t)arg3);
 
     case KEYCTL_WATCH_KEY:
         return keyctl_watch_key((key_serial_t)arg2, (int)arg3, (int)arg4);
 
     default:
         return -EOPNOTSUPP;
     }
 }

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