libceph: refresh auth->authorizer_buf{,_len} after authorizer update

libceph: refresh auth->authorizer_buf{,_len} after authorizer update

ceph_x_create_authorizer() caches au->buf->vec.iov_base and
au->buf->vec.iov_len in struct ceph_auth_handshake.  These
cached values are then used by the messenger connect code when
sending the authorizer.

ceph_x_update_authorizer() can rebuild the authorizer when a newer
service ticket is available.  If the rebuilt authorizer no longer
fits in the existing buffer, ceph_x_build_authorizer() drops its
reference to au->buf and allocates a new one.  If this is the final
reference, ceph_buffer_put() frees the old ceph_buffer and its
vec.iov_base, but auth->authorizer_buf still points at that freed
memory.

A subsequent msgr1 reconnect can therefore queue the stale pointer
and trigger a KASAN slab-use-after-free in _copy_from_iter() while
tcp_sendmsg() copies the authorizer.

Refresh auth->authorizer_buf and auth->authorizer_buf_len after a
successful authorizer rebuild so the messenger sends the current
buffer.

Cc: stable@vger.kernel.org
Fixes: 0bed9b5c523d ("libceph: add update_authorizer auth method")
Closes: https://lore.kernel.org/all/E378850E-106C-427B-A241-970EB2D054D7@gmail.com/
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Reviewed-by: Alex Markuze <amarkuze@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>