KEYS: Don't permit request_key() to construct a new keyring

If request_key() is used to find a keyring, only do the search part - don't
do the construction part if the keyring was not found by the search.  We
don't really want keyrings in the negative instantiated state since the
rejected/negative instantiation error value in the payload is unioned with
keyring metadata.

Now the kernel gives an error:

	request_key("keyring", "#selinux,bdekeyring", "keyring", KEY_SPEC_USER_SESSION_KEYRING) = -1 EPERM (Operation not permitted)

Signed-off-by: David Howells <dhowells@redhat.com>
(cherry picked from commit 911b79cde95c7da0ec02f48105358a36636b7a71)

Orabug: 29304551
CVE: CVE-2017-17807

Reviewed-by: John Donnelly <John.p.donnelly@oracle.com>
Signed-off-by: Allen Pais <allen.pais@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 486ef6fa393b2cc9d8ceb8cb11f187f97730bd90..0d625312427831b63ed18784719cd0b424f03a41 100644 (file)
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -440,6 +440,9 @@ static struct key *construct_key_and_link(struct keyring_search_context *ctx,
 
        kenter("");
 
+       if (ctx->index_key.type == &key_type_keyring)
+               return ERR_PTR(-EPERM);
+       
        user = key_user_lookup(current_fsuid());
        if (!user)
                return ERR_PTR(-ENOMEM);