Re: [PATCH 2/2] ppc: kvm: use anon_inode_getfd() with O_CLOEXEC flag

[Yann Droneaud]

Le 26.08.2013 09:39, Paolo Bonzini a ÃcritÂ:
> Il 25/08/2013 17:04, Alexander Graf ha scritto:
> > On 24.08.2013, at 21:14, Yann Droneaud wrote:
> >
> > > This patch set O_CLOEXEC flag on all file descriptors created
> > > with anon_inode_getfd() to not leak file descriptors across exec().
> > >
> > > Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx>
> > > Link: 
> > > http://lkml.kernel.org/r/cover.1377372576.git.ydroneaud@xxxxxxxxxx
> >
> > Reviewed-by: Alexander Graf <agraf@xxxxxxx>
> >
> > Would it make sense to simply inherit the O_CLOEXEC flag from the
> > parent kvm fd instead? That would give user space the power to keep
> > fds across exec() if it wants to.
>
> Does it make sense to use non-O_CLOEXEC file descriptors with KVM at
> all?  Besides fork() not being supported by KVM, as described in
> Documentation/virtual/kvm/api.txt, the VMAs of the parent process go
> away as soon as you exec().  I'm not sure how you can use the inherited
> file descriptor in a sensible way after exec().

Sounds a lot like InfiniBand subsystem behavor: IB file descriptors
are of no use accross exec() since memory mappings tied to those fds
won't be available in the new process:

https://lkml.org/lkml/2013/7/8/380
http://mid.gmane.org/f58540dc64fec1ac0e496dfcd3cc1af7@xxxxxxxx

Regards.

--
Yann Droneaud
OPTEYA

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