Those flags are stickers. The note on this picture said

送交者: steven 于 2012-06-19, 18:20:49:

回答: OMG，我还以为多大的国旗呢。由 silxirt 于 2012-06-19, 17:38:41:

the flag stuck on Hu's shoe, and he tried to take care of it, and Obama gave him a hand. It wasn't that sensational as the Chinese article suggested.

Obama gave him a hand？？？？source?photo? - pgss (39 bytes) 2012-06-19, 23:57:39 (670259)
- the picture above shown Obama's hand on Hu's back - steven (102 bytes) 2012-06-20, 00:06:32 (670261)
- AP. (无内容) - steven (0 bytes) 2012-06-20, 00:02:48 (670260)