fscrypt: fix dereference of NULL user_key_payload
authorEric Biggers <ebiggers@google.com>
Mon, 9 Oct 2017 19:46:18 +0000 (12:46 -0700)
committerDavid Howells <dhowells@redhat.com>
Thu, 12 Oct 2017 16:16:40 +0000 (17:16 +0100)
commitd60b5b7854c3d135b869f74fb93eaf63cbb1991a
treebe7b147d0cb48d18f7069e053c4271dead139f94
parent192cabd6a296cbc57b3d8c05c4c89d87fc102506
fscrypt: fix dereference of NULL user_key_payload

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 <james.l.morris@oracle.com>
Cc: <stable@vger.kernel.org> [v4.1+]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
fs/crypto/keyinfo.c