[PATCH RFC] nsproxy: strengthen the comment above copy_namespaces

[PATCH RFC] nsproxy: strengthen the comment above copy_namespaces

[Serge E. Hallyn]

copy_namespaces() cannot be used on a live task.  There are two
reasons - it can be used to assign another task's nsproxy, which
is not legal (for a live task).  And, it does not use
rcu_assign_pointer, so even when we're being extra-clever it is
unsafe.

Signed-off-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 kernel/nsproxy.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f74e6c0..67d8f2b 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -115,6 +115,9 @@ out_ns:
 /*
  * called from clone.  This now handles copy for nsproxy and all
  * namespaces therein.
+ * Note this should only be used in fork.  Specifically, tsk should
+ * not yet be a live task.  See the the unshare code for how to handle
+ * that.
  */
 int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 {
-- 
1.6.3.3

Re: [PATCH RFC] nsproxy: strengthen the comment above copy_namespaces

[Oren Laadan]

Serge -

Is this intended for linux-cr ?
Sounds like it should go (or already?) upstream.

Oren.

On 04/30/2010 02:36 PM, Serge E. Hallyn wrote:
> copy_namespaces() cannot be used on a live task.  There are two
> reasons - it can be used to assign another task's nsproxy, which
> is not legal (for a live task).  And, it does not use
> rcu_assign_pointer, so even when we're being extra-clever it is
> unsafe.
> 
> Signed-off-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> ---
>  kernel/nsproxy.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index f74e6c0..67d8f2b 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -115,6 +115,9 @@ out_ns:
>  /*
>   * called from clone.  This now handles copy for nsproxy and all
>   * namespaces therein.
> + * Note this should only be used in fork.  Specifically, tsk should
> + * not yet be a live task.  See the the unshare code for how to handle
> + * that.
>   */
>  int copy_namespaces(unsigned long flags, struct task_struct *tsk)
>  {

Re: [PATCH RFC] nsproxy: strengthen the comment above copy_namespaces

[Serge E. Hallyn]

Quoting Oren Laadan (orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org):
> Serge -
> 
> Is this intended for linux-cr ?
> Sounds like it should go (or already?) upstream.

It was intended for upstream, bit i was fishing for acks/feedback
before pushing further.

> Oren.
> 
> On 04/30/2010 02:36 PM, Serge E. Hallyn wrote:
> > copy_namespaces() cannot be used on a live task.  There are two
> > reasons - it can be used to assign another task's nsproxy, which
> > is not legal (for a live task).  And, it does not use
> > rcu_assign_pointer, so even when we're being extra-clever it is
> > unsafe.
> > 
> > Signed-off-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> > ---
> >  kernel/nsproxy.c |    3 +++
> >  1 files changed, 3 insertions(+), 0 deletions(-)
> > 
> > diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> > index f74e6c0..67d8f2b 100644
> > --- a/kernel/nsproxy.c
> > +++ b/kernel/nsproxy.c
> > @@ -115,6 +115,9 @@ out_ns:
> >  /*
> >   * called from clone.  This now handles copy for nsproxy and all
> >   * namespaces therein.
> > + * Note this should only be used in fork.  Specifically, tsk should
> > + * not yet be a live task.  See the the unshare code for how to handle
> > + * that.
> >   */
> >  int copy_namespaces(unsigned long flags, struct task_struct *tsk)
> >  {
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