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authorDavid Howells <dhowells@redhat.com>2019-06-19 16:10:15 +0100
committerDavid Howells <dhowells@redhat.com>2019-06-19 16:10:15 +0100
commit896f1950e5944532b971d880a6bae7fba3b6a8d3 (patch)
tree8bf2eddc61af7f782bdd579e87fa0f7760ea5ced /Documentation/security
parente59428f721ee096d8a020504ea908a6f0d952735 (diff)
downloadlinux-896f1950e5944532b971d880a6bae7fba3b6a8d3.tar.bz2
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>
Diffstat (limited to 'Documentation/security')
-rw-r--r--Documentation/security/keys/core.rst10
-rw-r--r--Documentation/security/keys/request-key.rst9
2 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst
index 82dd457ff78d..003f1452a5b7 100644
--- a/Documentation/security/keys/core.rst
+++ b/Documentation/security/keys/core.rst
@@ -1147,6 +1147,16 @@ payload contents" for more information.
case error ERESTARTSYS will be returned.
+ * To search for a key under RCU conditions, call::
+
+ struct key *request_key_rcu(const struct key_type *type,
+ const char *description);
+
+ which is similar to request_key() except that it does not check for keys
+ that are under construction and it will not call out to userspace to
+ construct a key if it can't find a match.
+
+
* When it is no longer required, the key should be released using::
void key_put(struct key *key);
diff --git a/Documentation/security/keys/request-key.rst b/Documentation/security/keys/request-key.rst
index 07af991463b5..7caedc4d29f1 100644
--- a/Documentation/security/keys/request-key.rst
+++ b/Documentation/security/keys/request-key.rst
@@ -36,6 +36,11 @@ or::
size_t callout_len,
void *aux);
+or::
+
+ struct key *request_key_rcu(const struct key_type *type,
+ const char *description);
+
Or by userspace invoking the request_key system call::
key_serial_t request_key(const char *type,
@@ -57,6 +62,10 @@ The two async in-kernel calls may return keys that are still in the process of
being constructed. The two non-async ones will wait for construction to
complete first.
+The request_key_rcu() call is like the in-kernel request_key() call, except
+that it doesn't check for keys that are under construction and doesn't attempt
+to construct missing keys.
+
The userspace interface links the key to a keyring associated with the process
to prevent the key from going away, and returns the serial number of the key to
the caller.