KEYS: close race between key lookup and freeing
When a key is being garbage collected, it's key->user would get put before
the ->destroy() callback is called, where the key is removed from it's
respective tracking structures.
This leaves a key hanging in a semi-invalid state which leaves a window open
for a different task to try an access key->user. An example is
find_keyring_by_name() which would dereference key->user for a key that is
in the process of being garbage collected (where key->user was freed but
->destroy() wasn't called yet - so it's still present in the linked list).
This would cause either a panic, or corrupt memory.
Fixes CVE-2014-9529.
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/security/keys/gc.c b/security/keys/gc.c
index 9609a7f..c795237 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -148,12 +148,12 @@
if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
atomic_dec(&key->user->nikeys);
- key_user_put(key->user);
-
/* now throw away the key memory */
if (key->type->destroy)
key->type->destroy(key);
+ key_user_put(key->user);
+
kfree(key->description);
#ifdef KEY_DEBUGGING