KEYS: Make request key instantiate the per-user keyrings

Make request_key() instantiate the per-user keyrings so that it doesn't oops
if it needs to get hold of the user session keyring because there isn't a
session keyring in place.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Steve French <smfrench@gmail.com>
Tested-by: Rutger Nijlunsing <rutger.nijlunsing@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

security/keys/internal.h

@@ -107,6 +107,7 @@ extern key_ref_t search_process_keyrings(struct key_type *type,
 
 extern struct key *find_keyring_by_name(const char *name, bool skip_perm_check);
 
+extern int install_user_keyrings(struct task_struct *tsk);
 extern int install_thread_keyring(struct task_struct *tsk);
 extern int install_process_keyring(struct task_struct *tsk);
 

security/keys/process_keys.c

@@ -40,7 +40,7 @@ struct key_user root_key_user = {
 /*
  * install user and user session keyrings for a particular UID
  */
-static int install_user_keyrings(struct task_struct *tsk)
+int install_user_keyrings(struct task_struct *tsk)
 {
 	struct user_struct *user = tsk->user;
 	struct key *uid_keyring, *session_keyring;

security/keys/request_key.c

@@ -74,6 +74,10 @@ static int call_sbin_request_key(struct key_construction *cons,
 
 	kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
 
+	ret = install_user_keyrings(tsk);
+	if (ret < 0)
+		goto error_alloc;
+
 	/* allocate a new session keyring */
 	sprintf(desc, "_req.%u", key->serial);