libceph: handle rbtree insertion error in decode_choose_args()

libceph: handle rbtree insertion error in decode_choose_args()

A message of type CEPH_MSG_OSD_MAP contains an OSD map that itself
contains a CRUSH map. The received CRUSH map may optionally contain
choose_args that get decoded in decode_choose_args(). In this function,
num_choose_arg_maps is read from the message, and a corresponding number
of crush_choose_arg_maps gets decoded afterwards. Each
crush_choose_arg_map has a choose_args_index, which serves as the key
when inserting it into the choose_args rbtree of the decoded crush_map.
If a (potentially corrupted) message contains two crush_choose_arg_maps
with the same index, the assertion in insert_choose_arg_map() triggers a
kernel BUG when trying to insert the second crush_choose_arg_map.

This patch fixes the issue by switching to the non-asserting rbtree
insertion function and rejecting the message if the insertion fails.

[ idryomov: changelog ]

Cc: stable@vger.kernel.org
Signed-off-by: Raphael Zimmer <raphael.zimmer@tu-ilmenau.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>