Re: Fix compilation on Solaris 10

[Eric Blake]

On 2/28/19 7:38 AM, coypu@sdf.org wrote:
> Hi folks,
> 
> in Solaris 10 apparently O_CLOEXEC is not defined.
> (got a bug report in http://gnats.netbsd.org/54025)
> 
> Attached is a patch wrapping the code using it in #ifdef O_CLOEXEC.

Incomplete - if you are unable to atomically set the CLOEXEC flag during
open() due to lack of O_CLOEXEC, then you should use
fcntl(F_GETFD)/fcntl(F_SETFD) to set FD_CLOEXEC relatively soon after
the open(), so that the fd is still properly closed on forks either way.

In multi-threaded applications, O_CLOEXEC is essential to avoid data
races where one thread calls fork() in between another window calling
open() vs. fcntl() and thus inadvertently leaking the fd into the child;
but since bash is single-threaded, the race is only possible via signal
handlers, and hopefully bash isn't trying to fork from a signal handler
that might be interrupting the window between open() and fcntl().

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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