Commit f6a2c3d4 authored Oct 09, 2017 by Eric Biggers Committed by Greg Kroah-Hartman Oct 27, 2017

lib/digsig: fix dereference of NULL user_key_payload



commit 192cabd6a296cbc57b3d8c05c4c89d87fc102506 upstream.

digsig_verify() requests a user key, then accesses 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: 051dbb91 ("crypto: digital signature verification support")
Reviewed-by: James Morris <james.l.morris@oracle.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 400f063f

lib/digsig.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -86,6 +86,12 @@ static int digsig_verify_rsa(struct key *key,
		down_read(&key->sem);
		ukp = key->payload.data;

		if (!ukp) {
		/* key was revoked before we acquired its semaphore */
		err = -EKEYREVOKED;
		goto err1;
		}

		if (ukp->datalen < sizeof(*pkh))
		goto err1;