On Thu, 28 Sep 2017, Eric Biggers wrote:

From: Eric Biggers <redacted>

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")
Cc: <redacted>    [v4.1+]
Signed-off-by: Eric Biggers <redacted>

Reviewed-by: James Morris <redacted>


-- 
James Morris
[off-list ref]