2009-07-01 07:44:43

by Sukadev Bhattiprolu

Subject: [RFC][PATCH] Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination

Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination.

CLONE_PARENT was used to implement an older threading model. For consistency
with the CLONE_THREAD check in copy_pid_ns(), disable CLONE_PARENT and
CLONE_SIGHAND with CLONE_NEWPID, at least until the required semantics of
the pid namespaces are clear.

Changelog[v2]:
[Eric Biederman] Disable CLONE_SIGHAND also ???

Signed-off-by: Sukadev Bhattiprolu <[email protected]>
Acked-by: Roland McGrath <[email protected]>
---
kernel/pid_namespace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-mmotm/kernel/pid_namespace.c
===================================================================
--- linux-mmotm.orig/kernel/pid_namespace.c 2009-06-30 23:01:09.000000000 -0700
+++ linux-mmotm/kernel/pid_namespace.c 2009-06-30 23:49:06.000000000 -0700
@@ -118,7 +118,7 @@ struct pid_namespace *copy_pid_ns(unsign
{
if (!(flags & CLONE_NEWPID))
return get_pid_ns(old_ns);
- if (flags & CLONE_THREAD)
+ if (flags & (CLONE_THREAD|CLONE_PARENT|CLONE_SIGHAND))
return ERR_PTR(-EINVAL);
return create_pid_namespace(old_ns);
}

2009-07-02 01:31:56

by Serge E. Hallyn

Subject: Re: [RFC][PATCH] Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination

Quoting Sukadev Bhattiprolu ([email protected]):
>
> Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination.
>
> CLONE_PARENT was used to implement an older threading model. For consistency
> with the CLONE_THREAD check in copy_pid_ns(), disable CLONE_PARENT and
> CLONE_SIGHAND with CLONE_NEWPID, at least until the required semantics of
> the pid namespaces are clear.
>
> Changelog[v2]:
> [Eric Biederman] Disable CLONE_SIGHAND also ???
>
> Signed-off-by: Sukadev Bhattiprolu <[email protected]>
> Acked-by: Roland McGrath <[email protected]>

Acked-by: Serge Hallyn <[email protected]>

> ---
> kernel/pid_namespace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-mmotm/kernel/pid_namespace.c
> ===================================================================
> --- linux-mmotm.orig/kernel/pid_namespace.c 2009-06-30 23:01:09.000000000 -0700
> +++ linux-mmotm/kernel/pid_namespace.c 2009-06-30 23:49:06.000000000 -0700
> @@ -118,7 +118,7 @@ struct pid_namespace *copy_pid_ns(unsign
> {
> if (!(flags & CLONE_NEWPID))
> return get_pid_ns(old_ns);
> - if (flags & CLONE_THREAD)
> + if (flags & (CLONE_THREAD|CLONE_PARENT|CLONE_SIGHAND))
> return ERR_PTR(-EINVAL);
> return create_pid_namespace(old_ns);
> }

2009-07-02 12:00:41

by Oleg Nesterov

Subject: Re: [RFC][PATCH] Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination

On 07/01, Sukadev Bhattiprolu wrote:
>
> Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination.
>
> CLONE_PARENT was used to implement an older threading model. For consistency
> with the CLONE_THREAD check in copy_pid_ns(), disable CLONE_PARENT and
> CLONE_SIGHAND with CLONE_NEWPID, at least until the required semantics of
> the pid namespaces are clear.
>
> Changelog[v2]:
> [Eric Biederman] Disable CLONE_SIGHAND also ???
>
> Signed-off-by: Sukadev Bhattiprolu <[email protected]>
> Acked-by: Roland McGrath <[email protected]>
> ---
> kernel/pid_namespace.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-mmotm/kernel/pid_namespace.c
> ===================================================================
> --- linux-mmotm.orig/kernel/pid_namespace.c 2009-06-30 23:01:09.000000000 -0700
> +++ linux-mmotm/kernel/pid_namespace.c 2009-06-30 23:49:06.000000000 -0700
> @@ -118,7 +118,7 @@ struct pid_namespace *copy_pid_ns(unsign
> {
> if (!(flags & CLONE_NEWPID))
> return get_pid_ns(old_ns);
> - if (flags & CLONE_THREAD)
> + if (flags & (CLONE_THREAD|CLONE_PARENT|CLONE_SIGHAND))
> return ERR_PTR(-EINVAL);

Still can't understand why CLONE_SIGHAND is forbidden...

CLONE_SIGHAND doesn't mean we share the signal queue, so what is
the reason?

Oleg.

2009-07-11 19:39:27

by Sukadev Bhattiprolu

Subject: Re: [RFC][PATCH] Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination

Oleg Nesterov [[email protected]] wrote:
| On 07/01, Sukadev Bhattiprolu wrote:
| >
| > Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination.
| >
| > CLONE_PARENT was used to implement an older threading model. For consistency
| > with the CLONE_THREAD check in copy_pid_ns(), disable CLONE_PARENT and
| > CLONE_SIGHAND with CLONE_NEWPID, at least until the required semantics of
| > the pid namespaces are clear.
| >
| > Changelog[v2]:
| > [Eric Biederman] Disable CLONE_SIGHAND also ???
| >
| > Signed-off-by: Sukadev Bhattiprolu <[email protected]>
| > Acked-by: Roland McGrath <[email protected]>
| > ---
| > kernel/pid_namespace.c | 2 +-
| > 1 file changed, 1 insertion(+), 1 deletion(-)
| >
| > Index: linux-mmotm/kernel/pid_namespace.c
| > ===================================================================
| > --- linux-mmotm.orig/kernel/pid_namespace.c 2009-06-30 23:01:09.000000000 -0700
| > +++ linux-mmotm/kernel/pid_namespace.c 2009-06-30 23:49:06.000000000 -0700
| > @@ -118,7 +118,7 @@ struct pid_namespace *copy_pid_ns(unsign
| > {
| > if (!(flags & CLONE_NEWPID))
| > return get_pid_ns(old_ns);
| > - if (flags & CLONE_THREAD)
| > + if (flags & (CLONE_THREAD|CLONE_PARENT|CLONE_SIGHAND))
| > return ERR_PTR(-EINVAL);
|
| Still can't understand why CLONE_SIGHAND is forbidden...
|
| CLONE_SIGHAND doesn't mean we share the signal queue, so what is
| the reason?

I don't have a convincing reason. We could disable just the
CLONE_NEWPID|CLONE_PARENT combination till we have a need for it. We
talked about removing CLONE_PARENT but backed-off since some application
may be using it. Disabling specific combinations like this (CLONE_NEWPID is
relatively a new flag) could make it a little easier to remove CLONE_PARENT
in the future.

Sukadev