As far as North Korea, China has been accused of dragging her feet, but not of arming her.
Umm, sometimes, a little common sense goes a long long way.
http://fpc.state.gov/documents/organization/18223.pdf
http://www.uscc.gov/hearings/2006hearings/transcripts/sept_14/06_09_14_trans.pdf
Both are official US government reports.
About North Korea, it wouldn’t exist if it weren’t for Chinese help. Take one look at their military.