4.13-stable review patch. If anyone has any objections, please let me know.
------------------ From: Eric Biggers <[email protected]> commit d60b5b7854c3d135b869f74fb93eaf63cbb1991a upstream. When an fscrypt-encrypted file is opened, we request the file's master key from the keyrings service as a logon key, then access its payload. However, a revoked key has a NULL payload, and we failed to check for this. 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. Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities") Reviewed-by: James Morris <[email protected]> Signed-off-by: Eric Biggers <[email protected]> Signed-off-by: David Howells <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/crypto/keyinfo.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -109,6 +109,11 @@ static int validate_user_key(struct fscr goto out; } ukp = user_key_payload_locked(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + goto out; + } if (ukp->datalen != sizeof(struct fscrypt_key)) { res = -EINVAL; goto out;
