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keys: Provide request_key_rcu()
Provide a request_key_rcu() function that can be used to request a key under RCU conditions. It can only search and check permissions; it cannot allocate a new key, upcall or wait for an upcall to complete. It may return a partially constructed key. Signed-off-by: David Howells <dhowells@redhat.com>
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@ -1147,6 +1147,16 @@ payload contents" for more information.
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case error ERESTARTSYS will be returned.
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* To search for a key under RCU conditions, call::
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struct key *request_key_rcu(const struct key_type *type,
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const char *description);
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which is similar to request_key() except that it does not check for keys
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that are under construction and it will not call out to userspace to
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construct a key if it can't find a match.
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* When it is no longer required, the key should be released using::
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void key_put(struct key *key);
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@ -36,6 +36,11 @@ or::
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size_t callout_len,
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void *aux);
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or::
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struct key *request_key_rcu(const struct key_type *type,
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const char *description);
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Or by userspace invoking the request_key system call::
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key_serial_t request_key(const char *type,
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@ -57,6 +62,10 @@ The two async in-kernel calls may return keys that are still in the process of
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being constructed. The two non-async ones will wait for construction to
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complete first.
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The request_key_rcu() call is like the in-kernel request_key() call, except
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that it doesn't check for keys that are under construction and doesn't attempt
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to construct missing keys.
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The userspace interface links the key to a keyring associated with the process
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to prevent the key from going away, and returns the serial number of the key to
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the caller.
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@ -274,6 +274,9 @@ extern struct key *request_key(struct key_type *type,
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const char *description,
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const char *callout_info);
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extern struct key *request_key_rcu(struct key_type *type,
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const char *description);
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extern struct key *request_key_with_auxdata(struct key_type *type,
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const char *description,
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const void *callout_info,
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@ -756,3 +756,47 @@ struct key *request_key_async_with_auxdata(struct key_type *type,
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callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
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}
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EXPORT_SYMBOL(request_key_async_with_auxdata);
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/**
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* request_key_rcu - Request key from RCU-read-locked context
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* @type: The type of key we want.
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* @description: The name of the key we want.
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*
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* Request a key from a context that we may not sleep in (such as RCU-mode
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* pathwalk). Keys under construction are ignored.
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*
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* Return a pointer to the found key if successful, -ENOKEY if we couldn't find
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* a key or some other error if the key found was unsuitable or inaccessible.
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*/
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struct key *request_key_rcu(struct key_type *type, const char *description)
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{
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struct keyring_search_context ctx = {
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.index_key.type = type,
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.index_key.description = description,
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.index_key.desc_len = strlen(description),
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.cred = current_cred(),
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.match_data.cmp = key_default_cmp,
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.match_data.raw_data = description,
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.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
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.flags = (KEYRING_SEARCH_DO_STATE_CHECK |
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KEYRING_SEARCH_SKIP_EXPIRED),
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};
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struct key *key;
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key_ref_t key_ref;
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kenter("%s,%s", type->name, description);
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/* search all the process keyrings for a key */
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key_ref = search_process_keyrings_rcu(&ctx);
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if (IS_ERR(key_ref)) {
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key = ERR_CAST(key_ref);
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if (PTR_ERR(key_ref) == -EAGAIN)
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key = ERR_PTR(-ENOKEY);
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} else {
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key = key_ref_to_ptr(key_ref);
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}
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kleave(" = %p", key);
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return key;
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}
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EXPORT_SYMBOL(request_key_rcu);
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