[PATCH 3.16.y-ckt 069/118] KEYS: ensure we free the assoc array edit if edit is valid

[Luis Henriques]

3.16.7-ckt16 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Colin Ian King <colin.king at canonical.com>

commit ca4da5dd1f99fe9c59f1709fb43e818b18ad20e0 upstream.

__key_link_end is not freeing the associated array edit structure
and this leads to a 512 byte memory leak each time an identical
existing key is added with add_key().

The reason the add_key() system call returns okay is that
key_create_or_update() calls __key_link_begin() before checking to see
whether it can update a key directly rather than adding/replacing - which
it turns out it can.  Thus __key_link() is not called through
__key_instantiate_and_link() and __key_link_end() must cancel the edit.

CVE-2015-1333

Signed-off-by: Colin Ian King <colin.king at canonical.com>
Signed-off-by: David Howells <dhowells at redhat.com>
Signed-off-by: James Morris <james.l.morris at oracle.com>
Cc: Moritz Mühlenhoff <jmm at inutil.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 security/keys/keyring.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 9cf2575f0d97..860345cb05f1 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -1151,9 +1151,11 @@ void __key_link_end(struct key *keyring,
 	if (index_key->type == &key_type_keyring)
 		up_write(&keyring_serialise_link_sem);
 
-	if (edit && !edit->dead_leaf) {
-		key_payload_reserve(keyring,
-				    keyring->datalen - KEYQUOTA_LINK_BYTES);
+	if (edit) {
+		if (!edit->dead_leaf) {
+			key_payload_reserve(keyring,
+				keyring->datalen - KEYQUOTA_LINK_BYTES);
+		}
 		assoc_array_cancel_edit(edit);
 	}
 	up_write(&keyring->sem);