[PATCH 3.18, 4.4] libceph: handle an empty authorize reply

[Ilya Dryomov <idryomov@gmail.com>]

The authorize reply can be empty, for example when the ticket used to
build the authorizer is too old and TAG_BADAUTHORIZER is returned from
the service.  Calling ->verify_authorizer_reply() results in an attempt
to decrypt and validate (somewhat) random data in au->buf (most likely
the signature block from calc_signature()), which fails and ends up in
con_fault_finish() with !con->auth_retry.  The ticket isn't invalidated
and the connection is retried again and again until a new ticket is
obtained from the monitor:

  libceph: osd2 192.168.122.1:6809 bad authorize reply
  libceph: osd2 192.168.122.1:6809 bad authorize reply
  libceph: osd2 192.168.122.1:6809 bad authorize reply
  libceph: osd2 192.168.122.1:6809 bad authorize reply

Let TAG_BADAUTHORIZER handler kick in and increment con->auth_retry.

Cc: stable@vger.kernel.org
Fixes: 5c056fdc5b47 ("libceph: verify authorize reply on connect")
Link: https://tracker.ceph.com/issues/20164
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Sage Weil <sage@redhat.com>
[idryomov@gmail.com: backport to 4.4: extra arg, no CEPHX_V2]
---
 net/ceph/messenger.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 3e6897efe1eb..3ed2796d008b 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2049,15 +2049,19 @@ static int process_connect(struct ceph_connection *con)
 	dout("process_connect on %p tag %d\n", con, (int)con->in_tag);
 
 	if (con->auth_reply_buf) {
+		int len = le32_to_cpu(con->in_reply.authorizer_len);
+
 		/*
 		 * Any connection that defines ->get_authorizer()
 		 * should also define ->verify_authorizer_reply().
 		 * See get_connect_authorizer().
 		 */
-		ret = con->ops->verify_authorizer_reply(con, 0);
-		if (ret < 0) {
-			con->error_msg = "bad authorize reply";
-			return ret;
+		if (len) {
+			ret = con->ops->verify_authorizer_reply(con, 0);
+			if (ret < 0) {
+				con->error_msg = "bad authorize reply";
+				return ret;
+			}
 		}
 	}
 
-- 
2.19.2