lib/digsig: fix dereference of NULL user_key_payload
authorEric Biggers <ebiggers@google.com>
Mon, 9 Oct 2017 19:43:20 +0000 (12:43 -0700)
committerDavid Howells <dhowells@redhat.com>
Thu, 12 Oct 2017 16:16:40 +0000 (17:16 +0100)
commit192cabd6a296cbc57b3d8c05c4c89d87fc102506
tree493588074de865f887e0e4e4e5932de7fd82386f
parentd124b2c53c7bee6569d2a2d0b18b4a1afde00134
lib/digsig: fix dereference of NULL user_key_payload

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: 051dbb918c7f ("crypto: digital signature verification support")
Reviewed-by: James Morris <james.l.morris@oracle.com>
Cc: <stable@vger.kernel.org> [v3.3+]
Cc: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
lib/digsig.c