From: Sasha Levin Date: Mon, 29 Dec 2014 14:39:01 +0000 (-0500) Subject: KEYS: close race between key lookup and freeing X-Git-Tag: firefly_0821_release~176^2~2554^2~1 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a3a8784454692dd72e5d5d34dcdab17b4420e74c;p=firefly-linux-kernel-4.4.55.git 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 Signed-off-by: David Howells --- diff --git a/security/keys/gc.c b/security/keys/gc.c index 9609a7f0faea..c7952375ac53 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -148,12 +148,12 @@ static noinline void key_gc_unused_keys(struct list_head *keys) 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