which: standard output: Bad file number

[tux-mind]

when starting "which env" stdout pipe has some problems.

reported by @danktx

logcat: http://pastebin.com/raw.php?i=EYshJmff

[tux-mind]

in the same logcat the same command is started successfully.

there is 2 reason that can change a program behaviour:

• particular system state
• race condition

due to #5 the system is running out of file descriptors,
probably this is the reason why the child has it's stdout closed.

have to find a way to check pipes functionality before exec the target program.

[tux-mind]

problem was that:
dSploitd redirects stdout and stdin to /dev/null for child that does not use it.

on certain cases the open("/dev/null", O_RDWR) returns a file descriptor less then 3.
then we were using dup2(dev_null_fd, 1) redirect child stdout.

after that we close the dev_null_fd, but it's value is less then 3, so we are closing a previously duplicated fd.

i have to study another case:
if pipe has the same number of the target fd.