From fec442e32bf681ac6128952bf77f8936e250df2e Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 9 Oct 2017 12:37:49 -0700 Subject: KEYS: encrypted: fix dereference of NULL user_key_payload commit 13923d0865ca96312197962522e88bc0aedccd74 upstream. A key of type "encrypted" references a "master key" which is used to encrypt and decrypt the encrypted key's payload. However, when we accessed the master key's payload, we failed to handle the case where the master key has been revoked, which sets the payload pointer to NULL. Note that request_key() *does* skip revoked keys, but there is still a window where the key can be revoked before we acquire its semaphore. Fix it by checking for a NULL payload, treating it like a key which was already revoked at the time it was requested. This was an issue for master keys of type "user" only. Master keys can also be of type "trusted", but those cannot be revoked. Fixes: 7e70cb497850 ("keys: add new key-type encrypted") Reviewed-by: James Morris Cc: Mimi Zohar Cc: David Safford Signed-off-by: Eric Biggers Signed-off-by: David Howells Signed-off-by: Greg Kroah-Hartman diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index 8d9330a..dd1e642 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -315,6 +315,13 @@ static struct key *request_user_key(const char *master_desc, const u8 **master_k down_read(&ukey->sem); upayload = user_key_payload(ukey); + if (!upayload) { + /* key was revoked before we acquired its semaphore */ + up_read(&ukey->sem); + key_put(ukey); + ukey = ERR_PTR(-EKEYREVOKED); + goto error; + } *master_key = upayload->data; *master_keylen = upayload->datalen; error: -- cgit v0.10.2