Code: static int ceph_x_verify_authorizer_reply(struct ceph_auth_client *ac,
					  struct ceph_authorizer *a, size_t len)
{
	struct ceph_x_authorizer *au = (void *)a;
 	struct ceph_x_ticket_handler *th;
 	int ret = 0;
 	struct ceph_x_authorize_reply reply;
 	void *p = au->reply_buf;
 	void *end = p + sizeof(au->reply_buf);
 
 	th = get_ticket_handler(ac, au->service);
 	if (IS_ERR(th))
 		return PTR_ERR(th);
	ret = ceph_x_decrypt(&th->session_key, &p, end, &reply, sizeof(reply));
 	if (ret < 0)
 		return ret;
 	if (ret != sizeof(reply))
		return -EPERM;

	if (au->nonce + 1 != le64_to_cpu(reply.nonce_plus_one))
		ret = -EPERM;
	else
		ret = 0;
	dout("verify_authorizer_reply nonce %llx got %llx ret %d\n",
	     au->nonce, le64_to_cpu(reply.nonce_plus_one), ret);
	return ret;
}

Vulnerability Type: DoS 
CWE ID: CWE-399
Summary: net/ceph/auth_x.c in Ceph, as used in the Linux kernel before 3.16.3, does not properly validate auth replies, which allows remote attackers to cause a denial of service (system crash) or possibly have unspecified other impact via crafted data from the IP address of a Ceph Monitor.
Commit Message: libceph: do not hard code max auth ticket len

We hard code cephx auth ticket buffer size to 256 bytes.  This isn't
enough for any moderate setups and, in case tickets themselves are not
encrypted, leads to buffer overflows (ceph_x_decrypt() errors out, but
ceph_decode_copy() doesn't - it's just a memcpy() wrapper).  Since the
buffer is allocated dynamically anyway, allocated it a bit later, at
the point where we know how much is going to be needed.

Fixes: http://tracker.ceph.com/issues/8979

Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@redhat.com>