There appears to be a race between:
(1) key_gc_unused_keys() which frees key->security and then calls
keyring_destroy() to unlink the name from the name list
(2) find_keyring_by_name() which calls key_permission(), thus accessing
key->security, on a key before checking to see whether the key usage is 0
(ie. the key is dead and might be cleaned up).
Fix this by calling ->destroy() before cleaning up the core key data -
including key->security.
Reported-by: Petr Matousek <pmatouse@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>