Commit d60b5b78 authored Oct 09, 2017 by Eric Biggers Committed by David Howells Oct 12, 2017

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: 88bd6ccd ("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>

parent 192cabd6

fs/crypto/keyinfo.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -109,6 +109,11 @@ static int validate_user_key(struct fscrypt_info *crypt_info,
		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		/* key was revoked before we acquired its semaphore */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;

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