Re: [PATCH] [BZ #18433] Check file access/existence before forking.

[Mike Frysinger <vapier at gentoo dot org>]

On 14 Sep 2015 15:04, Szabolcs Nagy wrote:
> On 11/09/15 22:01, Zack Weinberg wrote:
> > On Fri, Sep 11, 2015 at 5:18 AM, Florian Weimer wrote:
> >>> All in all I am inclined to say leave things as they are.  Nobody uses
> >>> posix_spawn if they can help it, anyway :)
> >>
> >> We need to move people off fork and clone to posix_spawn.  If it is
> >> missing functionality, we should add it.
> >
> > ... I honestly have no idea why you say that.  I am under the
> 
> because fork has issues
> 
> - spawn process from a large application (memory overcommit off)
>    is unreliable with fork.
> - using it from a multi-threaded application (so from a library)
>    is hard, because the child has to be AS-safe.
> - leaks sensitive information to the child (the sensitive info
>    is often managed by a library and there is no way of safely
>    clearing it on fork).
> - pthread_atfork is broken, further limiting the applicability
>    of fork in multi-threaded code (it cannot be implemented if
>    fork has to be AS-safe and the interface contract of the
>    callbacks are ill-defined).
> - it has no simple implementation if the underlying platform has
>    no fork syscall with the right semantics (posix on windows,
>    nommu,...)

how does posix_spawn mangically fix these things ?  it still calls
fork internally, and the use of the vfork flag is non-portable.
-mike

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