[patch] Close fds before execute a cmd

[Stone, Joshua I]

Lai Jiangshan wrote:
> 	I traced this bug and at the last I found the reason: stapio did
not
> close some file descriptors before using execl() to run a cmd. The
> processes of this cmd may read or write on the fds inherited from
> stapio. Especially the fd of control_channel, if one of processes of
> this cmd reads and writes on this fd, it communicates with
> stap_XXXXXX.ko, and lots of BUGs occurred. (Does stap_XXXXXX.ko
> support communicating with two or more processes at the same time?)

It would be strange for an app to do anything on an already open fd, but
not unheard of, I suppose. 

Rather than brute-force closing all fd > 2, a better way might be to set
FD_CLOEXEC in the appropriate places.


Josh