[gamin] Close-on-exec flag

[Roland Lutz <rlutz hedmen org>]

Hi,

libgamin 0.1.10 does not seem to set the FD_CLOEXEC flag on the file 
descriptor opened in FAMOpen2.  The calling code can obviously set this 
flag using fcntl(2), but:

> Any time a file descriptor can come into existence without FD_CLOEXEC 
> being set on it, you have a race between thread A creating the file 
> descriptor and then setting FD_CLOEXEC and thread B doing a fork() and 
> exec().  If thread B 'wins' this race, it will inherit a new file 
> descriptor that does not have FD_CLOEXEC set and this file descriptor 
> will leak through the exec(). [1]

As a solution, libgamin could either set the FD_CLOEXEC flag (which can be 
safely re-set afterwards, if needed) or offer an option to the calling 
code whether to set FD_CLOEXEC, as for example pipe2(2) does.

Roland


[1] http://utcc.utoronto.ca/~cks/space/blog/unix/ForkFDsAndRaces